# Polarization and Glare



## Sylvanite

The topic of glare, and how light polarization affects it seems to crop up over and over - along with some common misconceptions.  I'd like to address a few of them here.

First off, just what is "glare"?  Glare is a strong direct reflection that distracts from, obscures or washes out details in your subject. Some direct reflection is not necessarily a bad thing.  It provides a visual cue to surface shape (what is known as a specular highlight).  Without a little glare, it's difficult to see the quality of a gloss finish.  Just how much is too much varies with the viewer.  Each of us has our own preference.  I've had photos where one person commented that he wanted to see more shine - but another complained about the glare.  So, don't worry about the naysayers.

Ok, I've used a term without defining it first, so let's back up and talk about different ways that an object can reflect light:
*Direct Reflection* occurs when light hitting it bounces off solely at the complementary angle (angle of incidence = angle of reflection).  This is typical of smooth surfaces.
*Diffuse Reflection* occurs when light is scattered.  When light hits a matte surface, it is reflected in a variety of angles.
  This distinction becomes important in photography, because the two types of reflection behave differently.  I'll explain more as we go.

Now, what is polarized light?  This is not easy to imagine, because the common analogies don't always work.  Nevertheless, if you think of light as waves, then the wave frequency determines color, the amplitude determines brightness, and the angle of the wave is its polarization.  "Polarized Light" consists of waves all aligned at the same angle.  Unpolarized light has equal amounts of waves at all different angles.  Partially polarized light is a mix of the two.

When unpolarized light meets a polarizing filter (or polarizing reflector), then the waves that align with the filter pass through.  The waves that are perpendicular get absorbed.  The waves that are at an angle to the filter are partially absorbed and partially transmitted - with the transmitted portion all aligned.  The result is that 50% of the light is blocked, and the remaining 50% is polarized.

When polarized light meets a polarizing filter, the effect depends on the relative angles of polarization.  If they are the same, then the light passes through unchanged (and undimmed).  If they are perpendicular, then the light is completely absorbed.  At other angles, the light is partially transmitted and repolarized in the direction of the filter.

This can be confusing, but it is necessary to understand when using polarizing filters in photography.

Almost all light sources produce unpolarized light.  That includes candles, the sun, and artificial lights (incandescent, fluorescent, and LED).

Although it's theoretically possible to make a polarizing diffuser, most diffusers *do not* polarize light.  Diffusers made for photography - including light tents - do not.  In fact, diffusers generally depolarize light (they scatter light, producing waves with differing orientations).  Think about it - a polarizing filter absorbs 50% of unpolarized light.  You wouldn't want a photo diffuser that cuts your light in half. 

A cloudy sky works similarly.  The water droplets scatter light randomly, yielding unpolarized light.  A blue sky, on the other hand, produces polarized light.  The blue color comes from the ozone layer which not only filters out the other colors, but also (because ozone molecules are electrically polarized) aligns the waves.

Reflection also affects polarization.  Even if the source light is unpolarized, the reflection may be.  Conversely, a polarized light can produce unpolarized reflections.  Remember the 2 types of reflections, diffuse and direct?  Well, diffuse reflections do not polarize light.  In fact, they typically depolarize it.  Direct reflections may or may not become polarized.  Conductive surfaces (such as metal) typically reflect whatever light hits them  neither polarizing nor depolarizing it.  Non-conductive surfaces (including water, gloss plastic and polished wood) typically produce a polarized direct reflection.

Whew!  That's a lot to get through.  What's important to realize though is that glare can be be either polarized or unpolarized.  If your light source is unpolarized, then glare off metal pen components will be unpolarized.  Glare off a wood or plastic pen barrel, however, might be.

If the glare is polarized, then a polarizing filter can reduce or remove it.  If the glare is unpolarized, however, then a polarizing filter will not.  If the glare is mixed, then a polarizing filter could reduce it on one part but not another.  

So, although a single polarizing filter on your camera lens might help control some glare, it is not a complete solution.

There is a technique called cross-polarization that some people use.  In this setup, you place a polarizing filter over your light source.  The diffuse reflections off your subject are depolarized.  The direct reflections off your subject are polarized - even if they are metal.  Now, a polarizing lens filter will remove the direct reflection (glare).  Cross-polarization can work quite well, but it does have its own limitations.  First off, it typically limits you to one light source (matching polarization can be difficult).  Secondly, the polarizing filter halves your light, so to achieve the same exposure, you'll need a brighter (more expensive) light.  The filter itself is an additional investment as well.  Finally, some subjects will repolarize the direct reflection in multiple orientations, so there are still situations that cross-polarization will not handle.

Fortunately, there are tools to manage glare besides polarization.  Since glare is really a matter of direct reflection - not polarization - then glare (polarized or unpolarized) can be controlled by manipulating the direct reflection.  The angle (or "family of angles") of illumination that produces direct reflection is generally small compared to the angles that produce diffuse reflection.  Therefore, you can control the glare by adjusting the relative brightness of the light(s) within that family of angles.  If you want to reduce glare, you can selectively lower the proportion of light coming from the direction that produces direct reflection.  Product photographers often use multiple lights and/or reflectors outside the family of angles of direct reflection, or place a "go-between" (a.k.a. "gobo") in front of a light blocking the family of angles that reduce glare.

That isn't as complicated as it may sound.  Check out http://www.penturners.org/forum/f24/pen-photography-putting-concept-into-practice-128555/ for and example of using a light tent and a go-between to achieve a picture with even illumination and a subtle shine-line.

I hope that helps,
Eric


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## BJohn

Whew that it also a lot to absorb, but Eric I for appreciate the information I have printed out all of you articles in the library and find them extremely interesting also.

Keep it coming.


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## edstreet

> a lot to absorb



Actually he went mild on the subject.


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## Sylvanite

It has been said (in another thread):


> I believe it is a bigger issue using a lite tent because of the tent Defuses or scatters the light causing the light to become polarized and then reflects the light inside the tent , which and again scatters the light causing the light to be polarized.
> 
> 
> 
> I'm sorry, but that is just plain wrong.  Light tents *do not* polarize light.  In fact, they depolarize it.
> 
> Click to expand...
> 
> 
> ( Sorry )
> Yes me too, I really don't care to disagree with someone who has great knowledge as yourself in the field of photograph .
> I really don't care to disagree with anyone at any time or place..
> 
> I have a passion for photography just as you do too.
> And wouldn't ( want ) to say anything that wasn't true or give advise that was bad.
> Problem being is I believe in what I am saying and I have links to help prove what I am saying, plus I have done my own personal tests on photographing subjects with a smooth surface.
> 
> (Logic and common sense )
> How does a light tent depolarize light ?
> 
> Not trying to bump heads but in all honesty the people who make polarized sunglasses would pay a fortune for that technology .
> 
> Light tents scatter light defusing or softening, and they reflect light '
> and now you are saying they depolarize light ?
> 
> I have never read that......... please show me a company who makes light tents that claim there tents depolarize light ?
> 
> As you said just plain wrong and really not logical.
> Light traveling at the speed it does travel at, crashing into the side of a light tent it would only be logical that the light at the point of being scattered could or would have some kind of static electricity or a electromagnetic wave or become polarized .
Click to expand...


Rather than continue that discussion there, where it is off-topic, I've decided to address the issue here, as it may help clear up confusion about just what "polarization" is, and when it does and does not occur.  So, in reply to:
*How does a light tent depolarize light ?*

The answer is simple.  The light tent walls scatter the incoming light rays randomly, not only in direction (which is what diffuses the light), but also in polarity.  The resulting light is diffuse and depolarized.  Here's an experiment you can perform to confirm that the tent wall depolarizes light:  Take 2 linear polarizing filters (you can use 2 CPL filters as well, but you must position them front-to-front).  Hold them up in front of you and look at your source light.  Now rotate one of the filters.  You'll notice that as you rotate it, the image will turn black in one orientation, and gray at 90 degrees off.  Now do the same thing, but with the two filters on opposite sides of a light tent wall (or any other photo diffuser).  You'll see that as you rotate the filter, the light level does not change.  That is because the tent wall / diffuser has depolarized the light.


*The people who make polarized sunglasses would pay a fortune for that technology.*

Sunglasses do not diffuse light.  If they did, you wouldn't be able to see through them.  Therefore the manufacturers don't care about the properties of diffusion.  Polarized sunglasses serve two purposes.  First (just like non-polarized sunglasses), they reduce the amount of light that passes through.  Second, they block more light (up to all of it) provided that light is already polarized perpendicularly to the axis of the sunglasses.  Now, it just so happens that the blinding reflection of sunlight off water is mainly polarized horizontally.  Therefore polarized sunglasses (which polarize vertically) are quite effective at eliminating that glare.  Glare, however, is not necessarily polarized.  Polarized sunglasses do not, for example, cut the sun's glare off chrome bumpers.  In that instance, polarized sunglasses are no better than non-polarized sunglasses.


*Light tents scatter light defusing or softening, and they reflect light and now you are saying they depolarize light?*

Yes.  Of course a light tent reflects some light - otherwise it would appear black.  Of course they diffuse light - that is their purpose.  "Scatter" and "soften" are simply other ways of saying diffuse.  I've explained the depolarization in answer 1 above.


*Please show me a company who makes light tents that claim there tents depolarize light ?*

I don't know of any photo diffuser (including light tents) manufacturer who makes any claim about polarization, so I can't show you one.  I will turn the question around though.  Can anybody show a company who claims that their photo diffuser (or light tent)  polarizes light?  I doubt one can be found, because (1) it is the nature of diffusion to depolarize light, and (2) if a diffuser _did_ include a polarizing filter, it would cut the light transmission by at least half.  That would certainly not be a desirable property.


*It would only be logical that the light at the point of being scattered could or would have some kind of static electricity or a electromagnetic wave or become polarized *

Smooth, non-conductive surfaces, such as water, gloss plastic, and highly polished wood _do_ tend to produce polarized direct reflections.  That is not, however the whole story.  Conductive surfaces, such as polished metal, typically reflect light without changing the polarization (polarized light yields a polarized reflection; unpolarized light yields an unpolarized reflection).  Both of those surfaces, as well as matte surfaces, also produce diffuse reflection.  Diffuse reflection (because it is diffuse) is primarily depolarized.  Think about it.  If all these reflections were polarized, then a polarizing filter would not only filter out the glare, it would render the entire photograph black.  The photographic technique of "cross polarization" only works _because_ diffuse reflection (diffusion) depolarizes light.
Let's talk about nature's polarizing and depolarizing filters:
*Blue sky.*  Ozone (O3) is an electrically polarized molecule.  They tend to align with each other in the ozone layer, making it an electrically polarized filter in the sky.  The size of the molecules selectively reflects light in the blue frequencies (while passing the reds) and the charge aligns the waves.  That is why the sky is blue and why the blue light is polarized.  Probably the most common photographic use of polarizing filters is to darken the blue sky, increasing contrast with the white clouds.


*Overcast sky.*  Although the water molecule (H2O) is also electrically polarized, tiny water droplets (which is what clouds are formed of) are not.  When light reflects off or passes through clouds, the droplets scatter (diffuse) the light in random polarization, yielding unpolarized light.  That is why polarizing filters do not darken clouds in the sky photos I mentioned above.  If you don't believe me, here's another experiment for you.  On an overcast day, look up at the cloud layer through a polarizing filter.  Rotate the filter and you'll see that the image remains equally bright.  That indicates that the diffusion of the clouds produces depolarized light.
I hope that was helpful,
Eric


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## bobleibo

Eric
I really appreciate all the time you have put into these tutorials. I'm learning a lot thru them as I get the time to spend on what I have come to call your lesson plan, even if I only get to study a little bit at a time. 
Thank you~
Bob


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## Sylvanite

*How to tell if a light source is polarized*

Here's an experiment you can perform to tell whether or not a light source is polarized:
Set your camera to full manual exposure mode and mount a polarizing filter on the lens.
Turn your source light on and place a linear polarizing filter (such as a pair of polarizing sunglasses) so that it partially obscures the light.
Take a series of 4 photographs (all using the same exposure settings), rotating the camera's polarizing filter roughly 45 degrees each time.
  If the light source is polarized, then you will see the image change in brightness noticeably - from white, to gray, to black, and back to gray (although not necessarily in that order).  

If the light source is not polarized, it will be equally bright in all 4 photos.  

The polarizing filter (sunglasses) serves as a control for the experiment.  That part of the image will be polarized (whether the source is or not).  You should see it change in intensity as you rotate the camera's polarizing filter.


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## Sylvanite

*Proof that a CFL light bulb produces unpolarized light*

I performed the above experiment with one of the CFL bulbs I use for pen photography.  This is how the images changed as I rotated the camera's polarizing filter:







You can clearly see that the polarizing sunglasses changed in intensity dramatically.  That part of the picture had polarized light.  The rest of the light bulb, however, is bright in all 4 photos.  The light bulb itself produces light that is *NOT* polarized.


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## Sylvanite

*Proof that an incandescent light bulb produces unpolarized light*

I performed the above experiment again, with an ordinary household incandescent light bulb.  This image shows how the photographs changed as I rotated the polarizing filter:






As with the CFL test, the sunglasses indicate the effect a polarized light would produce.  The bulb intensity, however, does not change.  Therefore the light produced by the incandescent bulb is *NOT* polarized.


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## Sylvanite

To round things out, I tried again, this time with a household LED flood light.  Here is the result:






Just as with the previous two experiments, the polarizing lens darkened as I rotated the camera's polarizing filter, but the bulb itself did not.  The light given off by the LED bulb is *NOT* polarized.


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## mark james

Your series on Photography is incredible!  These are a great asset for those in the membership that can utilize this guidance.

Thank you for your contribution.


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## farmer

*light*



Sylvanite said:


> To round things out, I tried again, this time with a household LED flood light.  Here is the result:
> 
> 
> 
> 
> 
> 
> Just as with the previous two experiments, the polarizing lens darkened as I rotated the camera's polarizing filter, but the bulb itself did not.  The light given off by the LED bulb is *NOT* polarized.


 
Eric in another thread you corrected me and said all light sources are polarized now you are say LED lighting isn't polarized if i understand this correctly?
If LED lighting isn't polarized maybe you retract your statement when you corrected me in another thread..

In one statement you said the sunglasses is linear polarized film.
I have to ask have you ever really worked with real Lineiar  polarized film in photography ?
I have never done these tests that you are doing, but I have been working with linear polarized  for a few years .

Truth is all the led lighting I looked up and studies said the LED lighting is polarized, At the same time i remember reading about LED light and it said it wasn't polarized.
So i geuss the best way is to figure all light sources is polarized light and the only way to get rid of polarized light is by filtering it.
Pens are round and you will always have a 90 degree  light reflection even if the light is not polarized.
Light reflection
Polarized reflection 
And UV reflections 

It still seems to get down to if the light source is reflected, as its reflected inside the bulb.
If the light source is reflected like every light source known to man is  polarized.
They say  the suns light is not polarized , but i have done product photographs outside and using a light tent outside to and to be honest that's when i bought my first studio lighting continuous florescent lighting kit.


From my understanding the only way to depolarize light is to filter it.


How do you know those glasses are made with linear polarized film ?

I the only glasses i have seen that reminds my of polarized film is the cheap ones like the 3d glasses you get at the movie theater.
You want to do real tests then use real linear polarized film.
If you don't have any pm me your address and i will send some so your experiment will apples to apples  Or 100 percent accurate because you are using the film some of the members here will be buying.

The real experiment is to do real product photographs, who cares what the light bulb looks like with or with out sunglasses over it.
What counts is the finish product.............

 You know i use a Cross polarization technic in my product photography.
I might be the only one in here that is hitting my products with a extreme amount of light. 640 ws 

If you look up polarization by scattering its clear at least to me that when light is scattered it becomes polarized.

To be honest the study of light is a little over my head.
I don't understand it all.
But I have been photographing exotic wood products with strobes and cross polarization.

Are my pictures coming out good or not.



I want members in here to really excel in there photography skills.
I don't care who is right or wrong  as long as our advise is helping members just getting into photography.
 i am going to be doing a thread very soon on Off shoe speed lighting on my picnic table  .
 (Single strobe ) or mono
I will be testing both with and with out linear film and a CPL.



PS 
When light is  polarized is scattered ( defused reflected or softened )It becomes polarized , see polarization by scattering.


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## farmer

*Just read this in a photography forum.*

The weak colour is due to the LEDs, they don't provide a full colour spectrum, so won't render true colours, it'll be worse with red than any other colour. 

Photography on the net 
I quoted this out of a thread about photographing cars . 
I thought some of you might be interested in this statement.

Farmer 
Not much land D@m few cattle company


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## lorbay

I would love to spend a week with Eric just to gain a little more than what is in my pea brain. 
Lol

Lin


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## Sylvanite

farmer said:


> Eric in another thread you corrected me and said all light sources are polarized now you are say LED lighting isn't polarized if i understand this correctly?
> If LED lighting isn't polarized maybe you retract your statement when you corrected me in another thread..



To the best of my knowledge, I never said " all light sources are polarized".  In fact, in the initial post of this thread, I said "Almost all light sources produce unpolarized light. That includes candles, the sun, and artificial lights (incandescent, fluorescent, and LED)".  Please point me to the post you're referring to and I'll post a correction.



> In one statement you said the sunglasses is linear polarized film.
> I have to ask have you ever really worked with real Lineiar  polarized film in photography ?
> I have never done these tests that you are doing, but I have been working with linear polarized  for a few years .



I have not myself used "polarized film" in photography, but I am familiar with linear polarizers, circular polarizers (which is a linear polarizer combined with a quarter-wave plate; it first polarizes linearly and then converts linear polarization to  helical polarization) and with the technique of photographic "cross polarization".  If you are not convinced that the sunglasses yield linear polarization, then please _do_ try these tests yourself with linear polarizing film.  I'm confident that the results will be the same.



> Truth is all the led lighting I looked up and studies said the LED lighting is polarized, At the same time i remember reading about LED light and it said it wasn't polarized.



Are you perhaps confusing LED light with LCD light?  LCDs work by polarization.  LEDs do not.



> So i geuss the best way is to figure all light sources is polarized light and the only way to get rid of polarized light is by filtering it.



If "all light sources is polarized light" (sic) were true, then a polarizing filter, when aligned, would block all the light and the entire photo would be black - not just the glare.  I'm sure you realize that it doesn't work that way.



> Pens are round and you will always have a 90 degree  light reflection even if the light is not polarized.
> Light reflection
> Polarized reflection
> And UV reflections



A light shining on a reflective cylinder will reflect some light at a 90 degree angle. (and every other angle from 0 to 180 degrees too).  That reflection may or may not be polarized, and may or may not contain UV wavelengths.  And if it does, so what?



> It still seems to get down to if the light source is reflected, as its reflected inside the bulb.
> If the light source is reflected like every light source known to man is  polarized.



Not true.  The experiment photos above demonstrate that the light emitted from the bulbs (no matter how much they were reflected internally) is not polarized.  Many (most) light sources "known to man" are _NOT_ polarized.

Reflection does not necessarily polarize light.  Sometimes it does; sometimes it does not.  As I said earlier, diffuse reflection does not polarize light - it depolarizes it.  Direct reflection off non-conductive surfaces generally _does_ polarize light but direct reflection off conductive surfaces typically maintains its polarity (that is the reflection neither polarizes nor depolarizes the light).



> They say  the suns light is not polarized



That is correct.  Direct sunlight is not polarized.



> From my understanding the only way to depolarize light is to filter it.



A polarizing filter does not depolarize light.  It does the exact opposite.  A polarizing filter absorbs light waves that are electrically perpendicular its axis of polarity.  It passes light waves that are aligned with that axis.  It will polarize un-polarized light.  It will not depolarize polarized light.  Diffusion _will_ depolarize light  Any scattering that randomly orients the light waves' polarity depolarizes light.



> How do you know those glasses are made with linear polarized film ?



Polarizing sunglasses _are_ linear polarizers - that is how they work.  Whether or not they are constructed from "film" is irrelevant.  Are you really claiming that polarizing sunglasses do not polarize light?  If not, how do you think they work?



> You want to do real tests then use real linear polarized film.



Polarizing sunglasses are real linear polarizers.  The photos above demonstrate that.  Specialty films will produce the same result.



> The real experiment is to do real product photographs, who cares what the light bulb looks like with or with out sunglasses over it.
> What counts is the finish product.............



I'll be getting to pen photos.  I'm starting off with photos of the lights to dispel the myth that studio lamps produce polarized light.  



> You know i use a Cross polarization technic in my product photography.
> I might be the only one in here that is hitting my products with a extreme amount of light. 640 ws



The absolute amount of light is irrelevant.  I've photographed pens using three monolights  (totaling 600 ws) and using 2 26w CFL lights.  Others here have posted pen photographs lit with only a flashlight.  The only difference the absolute number of lumens makes is the shutter speed needed for proper exposure.



> If you look up polarization by scattering its clear at least to me that when light is scattered it becomes polarized.



Polarization by air scattering _does_ occur, but only at a specific and very small range of angles.  All other angles do not produce significant polarization.  The angles that produce polarization do not typically occur in studio photography (I've never seen it at all).

By means of analogy, rainbows are produced by refraction through atmospheric water at a certain angle.  Saying that all light that that is diffused or reflected becomes polarized is like saying that all light that that is refracted becomes rainbows.  Practical observation, however, clearly shows that neither is assertion is true.



> I want members in here to really excel in there photography skills.
> I don't care who is right or wrong  as long as our advise is helping members just getting into photography.



I also want to help people improve their photographic skills.  That's why I'm spending so much time and effort trying to correct misinformation.



> I will be testing both with and with out linear film and a CPL.



Please *do* perform the above experiments for yourself.  You don't even need to use the polarizing film.  The sunglasses are just there to demonstrate that the Circular Polarizing Filter on the camera was doing its job.  Put a CPL filter on your lens, and look through the viewfinder at your light source while rotating it.  If the light source is polarized, your image will at some point turn black.  If turning the filter doesn't change the intensity, then the light isn't linearly polarized.



> When light is  polarized is scattered ( defused reflected or softened )It becomes polarized , see polarization by scattering.



Again, the scattering that can cause polarization occurs at a very small range of angles that simply are not encountered in studio photography.  It's a mistake to read "can be polarized at one angle" as "is always polarized at all angles".

Sincerely,
Eric


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## Sylvanite

*Some light sources ARE polarized*

I've shown three light sources (fluorescent, incandescent, and LED) that produce unpolarized light.  Now here's one that _is_ polarized:






This is the LCD screen on a tablet.  Note that as the cameras polarizing filter (CPL in this case) is rotated, that the screen brightness changes as well as the brightness as seen through the polarizing sunglasses.  That demonstrates that the light emitted by the LCD display _is_ linearly polarized.

Now, we don't often use LCD lighting for pen photos, but people _have_ posted pen photos taken on a LCD background.  See http://www.penturners.org/forum/f24/unusual-small-item-photography-setup-94007/ for an example.  If one tried to use a CPL filter to control glare on a pen sitting on such a background, unexpected results might occur.

Note, not all LCD displays exhibit this phenomenon.  My LCD TV, for example, does not.  I believe that's because it incorporates a form of quarter-wave plate over the LCD layer.  That changes the linear polarization to helical (or "circular") polarization (just like a CPL filter does for a camera - although for a different purpose).


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## farmer

*photography*

 Quote Eric
I have not myself used "polarized film" in photography, but I am familiar with linear polarizers, circular polarizers (which is a linear polarizer combined with a quarter-wave plate; it first polarizes linearly and then converts linear polarization to  helical polarization) and with the technique of photographic "cross polarization".  If you are not convinced that the sunglasses yield linear polarization, then please _do_ try these tests yourself with linear polarizing film.  I'm confident that the results will be the same.
 Straight up I will send you some polarized film as long as You don't need a big piece ..........................


I have never used Linear polarized film on anything except flash or strobe lighting.

I would prefer that tests or experiments that we do can be done with the linear polarized film that is used in photography..

I am getting ready to shut down for the evening,
I will read the rest of everything you wrote.

I also will have to crack the books open and start looking things back up on line.
I  will do my best to either post links or page numbers of the same book we both own.

I don't know how you can do a accurate and honest tests on reflection and linear polarized film in photography when you don't own any linear polarized film.
This is not a dig, but to keep things simple and this thread is about polarization and reflection you need some linear polarized film.
Or you need a big pair of sun glasses that will fit or cover one or more of your lights.


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## Sylvanite

farmer said:


> I don't know how you can do a accurate and honest tests on reflection and linear polarized film in photography when you don't own any linear polarized film.


So far, I've posted no tests on reflection.  So far, I have not said my tests were with polarized "film".  I have used polarizing sunglasses.  Polarized film and polarizing sunglasses are both examples of linear polarizers.

And, in the experiments I've posted above, the polarizers are just the control, not the test.  All the sunglasses do is verify that the CPL orientation is different in each individual photograph.  The actual test is that the brightness of the un-obscured portion of the light bulb did not vary as I rotated the CPL filter.  You're objecting to the wrong part of the experiment.



> I would prefer that tests or experiments that we do can be done with the linear polarized film that is used in photography.



The tests certainly *CAN* be done with any linear polarizer - including linear polarizing film.  In fact, they can be done without any linear polarizer at all - just the CPL filter on the camera lens.  I encourage you to try it for yourself.



> I have never used Linear polarized film on anything except flash or strobe lighting.


  Then do the experiment with your monolight.  I'm sure you'll find that it produces light that is _not_ polarized (with or without the softbox).  Think about it - if the strobe, the softbox reflector, or the softbox cover (diffuser) did indeed polarize the light, then you wouldn't need the polarizing film at all.


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## Sylvanite

*Proof that polarizing sunglasses are a Linear Polarizing Filter*

I set up the following 4 photos (combined into one image) to demonstrate that the pair of polarizing sunglasses that I'm using is indeed a linear polarizing filter:






*Image 1*, in the upper left corner:In this photograph, I've arranged two photographic linear polarizing filters with a little bit of space between them.  The rear one is turned to block light that is vertically polarized.  The front one is turned to block light that is horizontally polarized.  Where they overlap, they block all light.  The card behind them is lit with unpolarized light.​*Image 2*, in the upper right corner:Here, I've place the polarizing sunglasses in between the two photo filters, oriented horizontally.  You can see that this matches the polarizing angle of the front filter.  Where it overlaps the rear filter, the image is black.​*Image 3*, in the lower left corner:In this photo, the sunglasses are between the photo filters, but oriented vertically.  This matches the polarizing angle of the rear filter.  Where it overlaps the front filter, the image is black.​*Image 4*, in the lower right corner:And, finally, I've oriented the sunglasses (still between the photo filters) at an angle.  Now it does not match the polarizing angle of either filter.  The area where it overlaps both filters is now transparent (although dark).  You can read the ad (where it says "Nikon") that was blacked out in photos 1-3.  This effect may seem counter-intuitive (after all, how is it possible that an additional filter could unblock light?), but it is real.  The rear filter converts unpolarized light into vertically polarized light (dimming it in the process).  The middle filter (the sunglasses) converts the vertically polarized light into light polarized at a 45 degree angle, and dims it further.  The front filter converts the 45 degree polarized light into horizontally polarized light (and dims it yet again).  Although each filter reduces the amount of light transmitted, some does indeed get through.​
A non-polarizing neutral density filter will not produce the above results.  It won't totally black out areas overlapped with a single polarizer like photos 2 and 3 do.    A circular polarizing filter will not produce the above results.  It will undo the linear polarization of one of the two outside filters (which one depends on which way the CPL is facing), yielding a result that is the same as using just 2 linear polarizing filters.  Quarter-wave plates can be combined to rotate polarized light by 90 degrees, but not 45 degrees as the sunglasses did in photo 4.

Only a linear polarizing filter will produce the effects shown above.  Therefore, the sunglasses' lenses are true linear polarizing filters.  They aren't "made for photography", but they work exactly the same way as a photographic linear polarizing filter does.

If you happen to have 3 photographic linear polarizing filters, or 2 CPL filters and one PL (you just have to put the CPLs on the outside and face-to-face), or 3 pieces of linear polarizing film, you can easily perform this experiment for yourself.

I hope that helps,
Eric


----------



## farmer

*UN real*

Just got done putting in a couple hrs on a reply and my internet stopped working and lost everything.'
What a waist of time ..


----------



## Sylvanite

*Proof that a light tent does not polarize light.*

Ok, enough about the polarity of various light sources.  It has been said that diffusion of light  polarizes it; that simply passing through a light tent will polarize light.  Here's a set of photographs showing that it isn't so:






The above 4 images show an illuminated light tent wall photographed through a circular polarizing (CPL) filter rotated in (roughly) 45 degree increments.  Each one was taken with the same exposure.  You can plainly see that the tent wall (the white background) luminosity remains constant.

If the diffuser (tent wall) had polarized the light, then it would have darkened to black, just like the polarizing sunglasses lens did (in the photo in the lower left corner).  The angle of the CPL, howevver, made no difference.  Therefore, diffusion in general, and a light tent wall in specific, does *NOT* polarize light.


----------



## Sylvanite

*Proof that a light tent actually depolarizes light.*

I've claimed in the past that not only does diffusion _not_ polarize light, that in actually de-polarizes it.  Here is an image to support that assertion.  I placed a linear polarizing filter (polarizing sunglasses again) immediately behind my light tent wall, through a pair of openings in the front.






As before, these four photos were shot at the same exposure with a circular polarizing (CPL) filter on the camera lens rotated in approximately 45 degree increments.  You can see that as I changed the polarization axis of the filter, the exposed part of the sunglasses turned dark - all the way to black.  The covered areas, however, did not change in intensity.  There is a shadow showing, but it is pretty constant in all 4 pictures.  If the light tent wall passed light without affecting polarity, then the area covering the sunglasses would have turned black along with the unobscured lens (lower left photo).  If the tent wall had changed the polarity, then one of the other 3 photos would have turned black (or at least much, much darker).  They didn't.

Because the light striking the inside of the tent wall was polarized (by the sunglasses), but the light exiting from the tent wall was not, I conclude that the light tent (via diffusion) depolarized the light.


----------



## farmer

*What cause light to be polairized*

There are 4 things that cause light to be polarized.
So if any of use do any of these four things to the light we are using in our pen photography you have polarized light and polarized reflection in your pictures.

It is possible to transform unpolarized light into *polarized light*. Polarized light waves are light waves in which the vibrations occur in a single plane. The process of transforming unpolarized light into polarized light is known as *polarization*. There are a variety of methods of polarizing light. The four methods discussed on this page are:
Polarization by Transmission
Polarization by Reflection
Polarization by Refraction
Polarization by Scattering

*The question is, is the light you are using in your photography is polarized or un-polarized when the light strikes the pen or the smooth surfaced nonmetallic subject.*
** 
*First off we must ask is the light we are using emitting electromagnetic polarized waves  before we soften or defuse the light.*
*Most lighting is not polarized ( Note I didn't say all lighting )*
*But Florescent lighting is polarized light which isn't a big deal considering that by time any of us get done defusing the light source and by time the light strikes the pen its polarized.*

* But first lets prove that florescent lighting is electromagnetic polarized light..............*

*Well wiki says florescent lighting is polarized !*
https://en.wikipedia.org/wiki/Fluorescence_anisotropy
*Fluorescence anisotropy* is the phenomenon where the light emitted by a fluorophore has unequal intensities along different axes of polarization. Early pioneers in the field include Aleksander Jablonski, Gregorio Weber,[1] and Andreas Albrecht.[2] The principles of fluorescence polarization and some applications of the method are presented in Lakowicz's book.

I see no reason to debate if florescent lighting is polarized light or un polarized any more, it clearly states that florescent lighting is polarized ...

Next as photographer are we making the light we use polarized ?

Well if you are doing the following things then you may not know it regard less of what lighting you are using.
 But in most cases I would have to say that everyone in here is using polarized light inless you are doing bare bulb photography
and here is my proof. 
You guys might really want to read this because color is involved in this too............
Polarization

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Polarization 
Light Waves and Color - Lesson 1 - How Do We Know Light is a Wave?
*Polarization*


Wavelike Behaviors of Light
Two Point Source Interference
Thin Film Interference
Polarization


A light wave is an electromagnetic wave that travels through the vacuum of outer space. Light waves are produced by vibrating electric charges. The nature of such electromagnetic waves is beyond the scope of The Physics Classroom Tutorial. For our purposes, it is sufficient to merely say that an electromagnetic wave is a transverse wave that has both an electric and a magnetic component.





The transverse nature of an electromagnetic wave is quite different from any other type of wave that has been discussed in The Physics Classroom Tutorial. Let's suppose that we use the customary slinky to model the behavior of an electromagnetic wave. As an electromagnetic wave traveled towards you, then you would observe the vibrations of the slinky occurring in more than one plane of vibration. This is quite different than what you might notice if you were to look along a slinky and observe a slinky wave traveling towards you. Indeed, the coils of the slinky would be vibrating back and forth as the slinky approached; yet these vibrations would occur in a single plane of space. That is, the coils of the slinky might vibrate up and down or left and right. Yet regardless of their direction of vibration, they would be moving along the same linear direction as you sighted along the slinky. If a slinky wave were an electromagnetic wave, then the vibrations of the slinky would occur in multiple planes. Unlike a usual slinky wave, the electric and magnetic vibrations of an electromagnetic wave occur in numerous planes. A light wave that is vibrating in more than one plane is referred to as *unpolarized light*. Light emitted by the sun, by a lamp in the classroom, or by a candle flame is unpolarized light. Such light waves are created by electric charges that vibrate in a variety of directions, thus creating an electromagnetic wave that vibrates in a variety of directions. This concept of unpolarized light is rather difficult to visualize. In general, it is helpful to picture unpolarized light as a wave that has an average of half its vibrations in a horizontal plane and half of its vibrations in a vertical plane.
It is possible to transform unpolarized light into *polarized light*. Polarized light waves are light waves in which the vibrations occur in a single plane. The process of transforming unpolarized light into polarized light is known as *polarization*. There are a variety of methods of polarizing light. The four methods discussed on this page are:

Polarization by Transmission
Polarization by Reflection
Polarization by Refraction
Polarization by Scattering
The way I understand this if you are doing any one of the 4 ways to polarized light in your photography then you have polarized light.

Personally if I understand all this correctly I am doing all four in my photography .

But lets go though this one at a time.
Polarization 

A light wave is an electromagnetic wave that travels through the vacuum of outer space. Light waves are produced by vibrating electric charges. The nature of such electromagnetic waves is beyond the scope of The Physics Classroom Tutorial. For our purposes, it is sufficient to merely say that an electromagnetic wave is a transverse wave that has both an electric and a magnetic component.





The transverse nature of an electromagnetic wave is quite different from any other type of wave that has been discussed in The Physics Classroom Tutorial. Let's suppose that we use the customary slinky to model the behavior of an electromagnetic wave. As an electromagnetic wave traveled towards you, then you would observe the vibrations of the slinky occurring in more than one plane of vibration. This is quite different than what you might notice if you were to look along a slinky and observe a slinky wave traveling towards you. Indeed, the coils of the slinky would be vibrating back and forth as the slinky approached; yet these vibrations would occur in a single plane of space. That is, the coils of the slinky might vibrate up and down or left and right. Yet regardless of their direction of vibration, they would be moving along the same linear direction as you sighted along the slinky. If a slinky wave were an electromagnetic wave, then the vibrations of the slinky would occur in multiple planes. Unlike a usual slinky wave, the electric and magnetic vibrations of an electromagnetic wave occur in numerous planes. A light wave that is vibrating in more than one plane is referred to as *unpolarized light*. Light emitted by the sun, by a lamp in the classroom, or by a candle flame is unpolarized light. Such light waves are created by electric charges that vibrate in a variety of directions, thus creating an electromagnetic wave that vibrates in a variety of directions. This concept of unpolarized light is rather difficult to visualize. In general, it is helpful to picture unpolarized light as a wave that has an average of half its vibrations in a horizontal plane and half of its vibrations in a vertical plane.
It is possible to transform unpolarized light into *polarized light*. Polarized light waves are light waves in which the vibrations occur in a single plane. The process of transforming unpolarized light into polarized light is known as *polarization*. There are a variety of methods of polarizing light. The four methods discussed on this page are:

Polarization by Transmission
Polarization by Reflection
Polarization by Refraction
Polarization by Scattering
 
*Polarization by Use of a Polaroid Filter*

The most common method of polarization involves the use of a *Polaroid filter*. Polaroid filters are made of a special material that is capable of blocking one of the two planes of vibration of an electromagnetic wave. (Remember, the notion of two planes or directions of vibration is merely a simplification that helps us to visualize the wavelike nature of the electromagnetic wave.) In this sense, a Polaroid serves as a device that filters out one-half of the vibrations upon transmission of the light through the filter. When unpolarized light is transmitted through a Polaroid filter, it emerges with one-half the intensity and with vibrations in a single plane; it emerges as polarized light.




A Polaroid filter is able to polarize light because of the chemical composition of the filter material. The filter can be thought of as having long-chain molecules that are aligned within the filter in the same direction. During the fabrication of the filter, the long-chain molecules are stretched across the filter so that each molecule is (as much as possible) aligned in say the vertical direction. As unpolarized light strikes the filter, the portion of the waves vibrating in the vertical direction are absorbed by the filter. The general rule is that the electromagnetic vibrations that are in a direction parallel to the alignment of the molecules are absorbed.
The alignment of these molecules gives the filter a *polarization axis*. This polarization axis extends across the length of the filter and only allows vibrations of the electromagnetic wave that are parallel to the axis to pass through. Any vibrations that are perpendicular to the polarization axis are blocked by the filter. Thus, a Polaroid filter with its long-chain molecules aligned horizontally will have a polarization axis aligned vertically. Such a filter will block all horizontal vibrations and allow the vertical vibrations to be transmitted (see diagram above). On the other hand, a Polaroid filter with its long-chain molecules aligned vertically will have a polarization axis aligned horizontally; this filter will block all vertical vibrations and allow the horizontal vibrations to be transmitted.




  Polarization of light by use of a Polaroid filter is often demonstrated in a Physics class through a variety of demonstrations. Filters are used to look through and view objects. The filter does not distort the shape or dimensions of the object; it merely serves to produce a dimmer image of the object since one-half of the light is blocked as it passed through the filter. A pair of filters is often placed back to back in order to view objects looking through two filters. By slowly rotating the second filter, an orientation can be found in which all the light from an object is blocked and the object can no longer be seen when viewed through two filters. What happened? In this demonstration, the light was polarized upon passage through the first filter; perhaps only vertical vibrations were able to pass through. These vertical vibrations were then blocked by the second filter since its polarization filter is aligned in a horizontal direction. While you are unable to see the axes on the filter, you will know when the axes are aligned perpendicular to each other because with this orientation, all light is blocked. So by use of two filters, one can completely block all of the light that is incident upon the set; this will only occur if the polarization axes are rotated such that they are perpendicular to each other.




  A picket-fence analogy is often used to explain how this dual-filter demonstration works. A picket fence can act as a polarizer by transforming an unpolarized wave in a rope into a wave that vibrates in a single plane. The spaces between the pickets of the fence will allow vibrations that are parallel to the spacings to pass through while blocking any vibrations that are perpendicular to the spacings. Obviously, a vertical vibration would not have the room to make it through a horizontal spacing. If two picket fences are oriented such that the pickets are both aligned vertically, then vertical vibrations will pass through both fences. On the other hand, if the pickets of the second fence are aligned horizontally, then the vertical vibrations that pass through the first fence will be blocked by the second fence. This is depicted in the diagram below.




  In the same manner, two Polaroid filters oriented with their polarization axes perpendicular to each other will block all the light. Now that's a pretty cool observation that could never be explained by a particle view of light.

I use a linear polarized filter on my strobes so a can only assume if I understand what was said above that in this cause I am actually polarizing the light.
Funny I didn't know that part , but I am using a cross polarization technic that my CPL will filter out polarized waves.



part 1 of 1











** 
**


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## farmer

*Part two, are we polarizing*

The second way to polarize light is.
*Polarization by Reflection*
Unpolarized light can also undergo polarization by reflection off of nonmetallic surfaces. The extent to which polarization occurs is dependent upon the angle at which the light approaches the surface and upon the material that the surface is made of. Metallic surfaces reflect light with a variety of vibrational directions; such reflected light is unpolarized. However, nonmetallic surfaces such as asphalt roadways, snowfields and water reflect light such that there is a large concentration of vibrations in a plane parallel to the reflecting surface. A person viewing objects by means of light reflected off of nonmetallic surfaces will often perceive a glare if the extent of polarization is large. Fishermen are familiar with this glare since it prevents them from seeing fish that lie below the water. Light reflected off a lake is partially polarized in a direction parallel to the water's surface. Fishermen know that the use of glare-reducing sunglasses with the proper polarization axis allows for the blocking of this partially polarized light. By blocking the plane-polarized light, the glare is reduced and the fisherman can more easily see fish located under the water.





   I know that when I soften light in side my soft box which is allot like a lite tent inside I am creating polarizing  light be cause I am reflecting it.
From this point I see no reason to debate if we reflect un polarized light will it become polarized or not.It clearly states above that it does.
 End or part 2


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## farmer

*Part 3 of what polarizes light*

*Polarization by Refraction*
Polarization can also occur by the refraction of light. Refraction occurs when a beam of light passes from one material into another material. At the surface of the two materials, the path of the beam changes its 
	

	
	
		
		

		
		
	


	




direction. The refracted beam acquires some degree of polarization. Most often, the polarization occurs in a plane perpendicular to the surface. The polarization of refracted light is often demonstrated in a Physics class using a unique crystal that serves as a double-refracting crystal. Iceland Spar, a rather rare form of the mineral calcite, refracts incident light into two different paths. The light is _split_ into two beams upon entering the crystal. Subsequently, if an object is viewed by looking through an Iceland Spar crystal, two images will be seen. The two images are the result of the double refraction of light. Both refracted light beams are polarized - one in a direction parallel to the surface and the other in a direction perpendicular to the surface. Since these two refracted rays are polarized with a perpendicular orientation, a polarizing filter can be used to completely block one of the images. If the polarization axis of the filter is aligned perpendicular to the plane of polarized light, the light is completely blocked by the filter; meanwhile the second image is as bright as can be. And if the filter is then turned 90-degrees in either direction, the second image reappears and the first image disappears. Now that's pretty neat observation that could never be observed if light did not exhibit any wavelike behavior.



*Watch It!*
​ In the demonstration below, the word PHUN (as in Physics is ...) is written on the glass panel of a classroom-style overhead projector. A sample of Iceland spar is placed over the word PHUN. Two images of the word PHUN can be faintly seen in the early seconds of the movie. The crystal double refracts light that passes through it. At about the 8-second mark, a Polaroid filter is placed over the crystal and rotated. As it rotates, the two images alternately fade in and out. The light passing through the crystal becomes polarized and when the Polaroid filter is rotated, it blocks and transmits the two light paths in alternating fashion. The result is that the two images of PHUN can be seen one at a time. Pretty cool stuff!

I am not sure on this one, some of my products have a thick looking clear finish on them and I am not sure if that would be considered refraction ? 

Part 3 of 4


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## farmer

*Part 4 of how to polarize light.*

And they say the sun light is not polarized .

*Polarization by Scattering*
Polarization also occurs when light is scattered while traveling through a medium. When light strikes the atoms of a material, it will often set the electrons of those atoms into vibration. The vibrating electrons then produce their own electromagnetic wave that is radiated outward in all directions. This newly generated wave strikes neighboring atoms, forcing their electrons into vibrations at the same original frequency. These vibrating electrons produce another electromagnetic wave that is once more radiated outward in all directions. This absorption and reemission of light waves causes the light to be scattered about the medium. (This process of scattering contributes to the blueness of our skies, a topic to be discussed later.) This scattered light is partially polarized. Polarization by scattering is observed as light passes through our atmosphere. The scattered light often produces a glare in the skies. Photographers know that this partial polarization of scattered light leads to photographs characterized by a _washed-out_ sky. The problem can easily be corrected by the use of a Polaroid filter. As the filter is rotated, the partially polarized light is blocked and the glare is reduced. The photographic secret of capturing a vivid blue sky as the backdrop of a beautiful foreground lies in the physics of polarization and Polaroid filters.

In photography personally I consider all light to be polarized.

OK I am done, I have stated my case, you guys can go about your photography the way you want to.
If you think the light you are using inside a light tent using florescent lighting is un - polarized then go ahead .
But the truth is the light inside a lite tent actually is polarized  and the above links 100 percent prove it...............

This may not be important but in reading  all this I found out that Electromagnet polarized waves will travel through walls ..........................


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## Sylvanite

farmer said:


> The question is, is the light you are using in your photography is polarized or un-polarized when the light strikes the pen or the smooth surfaced nonmetallic subject.



Well, the real question is whether or not the light reaching the camera is polarized, not whether or not the source light is, but the two are sometimes related, so to understand what's happening at the camera, you have to understand the light source.

Most pens we make have both metallic and nonmetallic components.  Reflective polarization behaves differently with conductive and non-conductive surfaces, so you need to consider more than just the nonmetallic parts.



> First off we must ask is the light we are using emitting electromagnetic polarized waves  before we soften or defuse the light.



Ok.



> Most lighting is not polarized ( Note I didn't say all lighting )



True.



> But Florescent lighting is polarized light



Not true.



> ... by time any of us get done defusing the light source and by time the light strikes the pen its polarized.



Not true.



> But first lets prove that florescent lighting is electromagnetic polarized light............
> Well wiki says florescent lighting is polarized !
> https://en.wikipedia.org/wiki/Fluorescence_anisotropy



You are making the same mistake you made with polarization by scattering.  That is, you're reading something that says a phenomenon can occur under some circumstances, and taking it to mean that....................... the phenomenon occurs under all circumstances.  That is incorrect.

Fluorescence anisotropy, in this case, occurs specifically when the fluorescing material is excited by *polarized* light.  When that occurs, the fluorescent light emitted is partially polarized.  If, however, the fluorescing material is excited by unpolarized light, then it produces unpolarized light.  The fluorescent light bulbs that we commonly use generate unpolarized UV light to excite the fluorescing material (the white coating on the inside of the bulb) which then emits unpolarized visible light.  



> I see no reason to debate if florescent lighting is polarized light or un polarized any more, it clearly states that florescent lighting is polarized ...



Again, it does _not_ state that _all_ fluorescent light is polarized.  It states that under very specific circumstances (which are not the circumstances we see in pen photography), that fluorescent light _can_ be partially polarized.  You are over-generalizing.



> Next as photographer are we making the light we use polarized ?
> 
> Well if you are doing the following things then you may not know it regard less of what lighting you are using.
> But in most cases I would have to say that everyone in here is using polarized light inless you are doing bare bulb photography
> and here is my proof.



I'm sorry.  I see a large quote copied from another site, but I don't see a proof.



> Polarization by Transmission
> Polarization by Reflection
> Polarization by Refraction
> Polarization by Scattering
> The way I understand this if you are doing any one of the 4 ways to polarized light in your photography then you have polarized light.



Again, these are ways in which light _can_ become polarized.  It does not mean that each one of them _always will_ polarize light.  It is entirely possible to (1) transmit, (2) reflect, (3) refract, and (4) scatter light *without* polarizing it.



> Personally if I understand all this correctly I am doing all four in my photography .
> 
> But lets go though this one at a time.



Once more, I see a large quote taken from another website, but no other explanation.



> I use a linear polarized filter on my strobes so a can only assume if I understand what was said above that in this cause I am actually polarizing the light.



Yes.  The strobe emits unpolarized light.  The silver lining in your softbox reflects unpolarized light.  The diffusing screen on the front of your softbox scatters unpolarized light. The linear polarizing film you hang over the softbox is what polarizes the light.

Think about it, if it were true that the flash, reflector, or diffuser polarized light, then you wouldn't need the polarizing film at all.



> Funny I didn't know that part , but I am using a cross polarization technic that my CPL will filter out polarized waves.



Ok, I'm confused.  How can you use cross-polarization in photography without knowing that linear polarizing film polarizes light?  

And, the way you say that makes me wonder if you realize that a CPL (circular polarizing) filter doesn't simply "filter out polarized waves".  It actually *is* a linear polarizing filter which polarizes the light in exactly the same way as the polarizing film does.  From a photographic effect standpoint, a linear polarizing (PL) filter is no different than a circular polarizing (CPL) filter.  The CPL filter simply has another layer on the back that converts the linear polarized light into helical (circular) polarized light.  This has no effect on the image that a camera sensor (or film) records, but eliminates problems in auto-focus and light metering that polarized light _may_ cause.

I suggest you go back and reread the source you just quoted, and pay particular attention to statements like:

_"Unpolarized light can also undergo polarization by reflection off of nonmetallic surfaces."_ and 
_"Polarization can also occur by the refraction of light"_

Note that they say "can", not "always does".  Note also that it specifically says says "nonmetallic" surfaces.  That should indicate to you that metallic reflections do not polarize light.  Note that the example they give for polarization by refraction uses a "unique crystal... Iceland Spar, a rather rare form of the mineral calcite".  That should tip you off that polarization by refraction is not an everyday occurrence.

The article you quoted (while not entirely complete) is accurate, but you are reading more into it than is there. 

Regards,
Eric


----------



## Sylvanite

farmer said:


> The second way to polarize light is.
> Polarization by Reflection
> ...
> I know that when I soften light in side my soft box which is allot like a lite tent inside I am creating polarizing  light be cause I am reflecting it.



Not true.



> From this point I see no reason to debate if we reflect un polarized light will it become polarized or not.It clearly states above that it does.



Read what you just quoted again.  It says:
_"Unpolarized light can also undergo polarization by reflection off of nonmetallic surfaces. "_
Note that it says "CAN", not "ALWAYS DOES".  Reflection does not always yield polarization.
_"The extent to which polarization occurs is dependent upon the angle at which the light approaches the surface and upon the material that the surface is made of."_
Note that polarization is angle dependent.  Only reflections at some angles become polarized.  Reflection at most angles does not polarize light.
_"Metallic surfaces reflect light with a variety of vibrational directions; such reflected light is unpolarized."_ 
This clearly says that metallic surfaces *do not* polarize light.  Take a look at the reflector in your softbox.  I think you will most likely find that it is metalized (silvered - although probably with aluminum).  The metallic surface will not polarize light at any angle.
If you take a moment to perform a simple test, such as I have shown above, you can easily determine whether or not your softbox polarizes light.

And, I'll ask again, if you believe that your softbox _does_ polarize light, then why do you bother putting a polarizing film over it?


----------



## Sylvanite

farmer said:


> I am not sure on this one, some of my products have a thick looking clear finish on them and I am not sure if that would be considered refraction ?


Look again at the text you just quoted.  It says:
_"Polarization can also occur by the refraction of light."_ 
It says "CAN", not "ALWAYS DOES".  

The circumstances under which refraction polarizes light are atypical.  That is why they have to resort to a _"unique crystal... Iceland Spar, a rather rare form of the mineral calcite"_ to demonstrate the effect.  I doubt you'll ever encounter significant polarization from refraction in a studio photography environment.

Think about it, a camera lens works by refraction.  If that refraction always polarized the light, then why would you bother putting a CPL (rather than just a PL) filter on your lens?  The refraction polarization would undo the circular polarization.  No, the reason you use a CPL rather than a PL filter is that the linear polarization produced by the PL persists through the refraction of the lens, and might interfere with a camera's light meter or auto-focus sensor.


----------



## walshjp17

Eric,

You should take all your excellent tutorials on pen photography and put them in a book.  I'm sure between IAP and FB you could find a ready market.


----------



## Sylvanite

farmer said:


> And they say the sun light is not polarized .


Direct sunlight _is not_ polarized.  Here's a simple  experiment you can perform in a spare moment to demonstrate that:

Take a piece (it doesn't have to be very big) of your photographic linear polarizing film outside on a sunny day and hold it such that you can see its shadow.  Now rotate it slowly through 180 degrees.  If the sunlight is polarized, you'll see the shadow disappear completely when the film's axis of polarization aligns with the sun's polarization, and  the shadow will darken to black when the film's axis is perpendicular to the sunlight's.  If the shadow does not lighten and darken as you rotate the film, then the sunlight does not have an axis of polarization - and therefore is not polarized.

Don't just read about it.  Try it for yourself.

I did it just now with a photographic polarizing filter.  As I rotated the filter, the shadow stayed the same shade of gray.



> In photography personally I consider all light to be polarized.


Then you're wrong.  I ask again, if all light is polarized, then why do you use polarizing film? 



> If you think the light you are using inside a light tent using florescent lighting is un - polarized then go ahead .



Yes, I believe that the light inside a light tent illuminated with fluorescent lights is unpolarized - and I've posted a series of photographs that demonstrate that fact above.



> But the truth is the light inside a lite tent actually is polarized  and the above links 100 percent prove it...............



No, it isn't, and no the links don't prove it.  The fact that light *CAN BECOME* polarized does not mean that it *ALWAYS IS* polarized.  In logical terms, you are attempting _proof by example_, which is fallacious.  

Atmospheric, or "Rayleigh" scattering (I know you know the name, because you quoted it previously) is only significant, and only polarizes light at angles approaching 90 degrees to the light source.  The effect is visible in the sky, but not in studio photography.  We don't illuminate our subject by pointing the studio light at the air beside it. 



> This may not be important but in reading  all this I found out that Electromagnet polarized waves will travel through walls



So, if as you say:
"I consider all light to be polarized", and 
"Electromagnet polarized waves will travel through walls", therefore
All light passes through walls
then you've just 100 percent proven that all walls are completely transparent - despite any examples to the contrary.  Is that true?


----------



## farmer

*Light*

Regardless if the light source is polarized or un polarized  I have soft boxes on my strobes,   < Polarization by Reflection > I soften my light, the light that is going through my soft boxes is being polarized because its being reflected and scattered ...Polarization by Scattering.
Then the light is filtered Polarization by Transmission which is really is separating the light.
The word polarize means to separate!, therefor the light that strikes the pen is polarized light.......................................

The only one out of the four I missed is Polarization by refraction.
.

Polarization by Transmission
Polarization by Reflection
Polarization by Scattering
Yes the suns light is partially polarized 
*Polarization by Scattering*
Polarization also occurs when light is scattered while traveling through a medium. When light strikes the atoms of a material, it will often set the electrons of those atoms into vibration. The vibrating electrons then produce their own electromagnetic wave that is radiated outward in all directions. This newly generated wave strikes neighboring atoms, forcing their electrons into vibrations at the same original frequency. These vibrating electrons produce another electromagnetic wave that is once more radiated outward in all directions. This absorption and reemission of light waves causes the light to be scattered about the medium. (This process of scattering contributes to the blueness of our skies, a topic to be discussed later.) This scattered light is partially polarized. Polarization by scattering is observed as light passes through our atmosphere. The scattered light often produces a glare in the skies. Photographers know that this partial polarization of scattered light leads to photographs characterized by a _washed-out_ sky. The problem can easily be corrected by the use of a Polaroid filter. As the filter is rotated, the partially polarized light is blocked and the glare is reduced. The photographic secret of capturing a vivid blue sky as the backdrop of a beautiful foreground lies in the physics of polarization and Polaroid filters.


----------



## Sylvanite

farmer said:


> Regardless if the light source is polarized or un polarized  I have soft boxes on my strobes,



Ok.



> I soften my light, the light that is going through my soft boxes is being polarized because its being reflected and scattered ...



Not so.  While reflection and atmospheric scattering CAN polarize light, they DO NOT ALWAYS polarize light.  The reflection inside the light box and the diffusion of the front screen are instances that DO NOT polarize light.  
Can you take a photograph demonstrating that your softbox emits polarized light? 


Can you explain why none of the photos in POST 20 - "Proof that a light tent does not polarize light" darkened if diffusion polarizes light?
I challenge you to do so.



> Then the light is filtered  which is really is separating the light.
> The word polarize means to separate!, therefor the light that strikes the pen is polarized light.......................................



The word "separate" is not synonymous with "polarize"  I can think of multiple ways to separate light without polarizing it.  Restating a false premise in different words does not make it true.



> The only one out of the four I missed is Polarization by refraction.


 
Actually, you didn't.  Your camera lens refracts light.



> Yes the suns light is partially polarized




Did you perform the experiment I described in POST 30?   If not, please do.  If so, did the shadow disappear (lighten) and darken as you rotated the film?  If not, explain why not. 


If, as you say, the reflection and diffusion inside the softbox polarize the light, then   why do you bother putting polarizing film over it?  The light exiting the softbox would already be polarized.


If the air in between the polarizing film and the subject polarize the light, then why did you need to use polarizing film before that?


If all the reflection off the subject is polarized, then why bother polarizing the light that hits the subject? 


If the air in between the subject and the camera lens polarizes the light, then why doesn't rotating the CPL filter opposite to its axis of polarization block all the light, and turn the image black?


If the refraction of the lens elements polarizes the light, then why did you bother using a CPL filter, rather than a plain PL filter on your lens?  Ditto for polarization by scattering of the air between the lens elements and in front of the sensor.
I challenge you to logically answer the above six questions.  And please give your explanation -- don't just copy text from another website and claim it supports your assertions.

Consider this quote (also from physicsclassroom.com):

*Rainbow Formation*:  A collection of suspended water droplets in the atmosphere serves as a refractor of light. The water represents a medium with a different optical density than the surrounding air. Light waves refract when they cross over the boundary from one medium to another. The decrease in speed upon entry of light into a water droplet causes a bending of the path of light towards the normal. And upon exiting the droplet, light speeds up and bends away from the normal. The droplet causes a deviation in the path of light as it enters and exits the drop.

Using the same logic you employed to describe polarization:

Rainbows are caused by the refraction of light waves.
Each of the elements in a camera lens refracts light waves.
Therefore they must each produce a rainbow.  
That proves 100 percent that every photograph ever taken must have at least one rainbow in it somewhere.
That conclusion is equally as valid, and just as incorrect as those you have made about polarization.


----------



## farmer

*Polaized light*

Answering your 6 questions.

1#Did you perform the experiment I described in POST 30?   If not, please do.  If so, did the shadow disappear (lighten) and darken as you rotated the film?  If not, explain why not. 

Answer
  No, I don't trust your experiments and I am not photographing sun glasses in a test when the lenses in sunglasses are not just linear polarized film, there is another thin film that goes over the linear polarized film used in sunglasses just for humans. This why I offered you Linear polarized film LPF used in  photography, I said in the beginning I wanted to use LPF that was used in product photography and production sets like TV .

 SEE 3D Movie glasses and sun glasses design.

#2 If, as you say, the reflection and diffusion inside the softbox polarize the light, then   why do you bother putting polarizing film over it?  The light exiting the softbox would already be polarized.

Answer
First its not me saying it, I am only repeating what it says about what causes polarization, that is why I have posted the link to polarization by reflection a half dozen times.
If you don't like what I am repeating then take it up with the experts.
Send comments to Wiki prove it to them.
Because I put my trust into someone who has to stand accountable in front of the science community, and we are not professors in anything.

Putting Linear polarized film  (LPF) over my soft boxes is the only place you can place it to get a cross polarization.
If I put the film inside the soft box the defuse panel ( white cloth ) over it.
It  would create polarized waves to travel at more then just a linear motion.


----------



## farmer

*PT 2 of answering questions*

Your Question 
#3
If the air in between the polarizing film and the subject polarize the light, then why did you need to use polarizing film before that?

My answer 
LOL  didn't we just go through this in question number 2 ?


# 4 
This is getting weird its the same question asked in three different ways.
I answered this question 2 questions ago.

#5 
If the air in between the subject and the camera lens polarizes the light, then why doesn't rotating the CPL filter opposite to its axis of polarization block all the light, and turn the image black?

My answer
The only way to polarize light between the camera and the subject would be if the light was colliding with something in the air.
Under those conditions I do not think I will be doing product photography on pens.
Reason being the only thing I can think of the would polarize the light would be dust .
And dust and product photography doesn't mix.

When the suns light finally strikes earth the light has been reflected off of space dust and that is why the suns light is partially polarized and our shy is blue.

Your talking polarization by scatting out of context ..

Thank God its Friday and this is the last questing :biggrin:

QUESTION # 6
If the refraction of the lens elements polarizes the light, then why did you bother using a CPL filter, rather than a plain PL filter on your lens?  Ditto for polarization by scattering of the air between the lens elements and in front of the sensor

I don't know, your the one who said lenses refract light and creates polarization inside the lens .
It could be the truth ? my TSE 17mm lens has over a dozen pieces of glass inside.

The way understood it the Polarization by refraction laws 
Is the light passes through something like glass then strikes a subject like our pen.
Because of the smooth non metallic surface that is where the reflection or glare is seen.

As far as I know humans don't see polarized light until is strikes a smooth non metallic surface like a pen.


----------



## Sylvanite

farmer said:


> 1#Did you perform the experiment I described in POST 30?   If not, please do.  If so, did the shadow disappear (lighten) and darken as you rotated the film?  If not, explain why not.
> 
> Answer
> No, I don't trust your experiments and I am not photographing sun glasses in a test when the lenses in sunglasses are not just linear polarized film, there is another thin film that goes over the linear polarized film used in sunglasses just for humans. This why I offered you Linear polarized film LPF used in  photography, I said in the beginning I wanted to use LPF that was used in product photography and production sets like TV .


Well, you've made it abundantly clear that you object to polarizing sunglasses (even though I demonstrated that they are linear polarizing filters exactly like those used in photography (which are by the way, different than 3D polarizing glasses).  That is why I:
performed the test you reference above with a photographic linear polarizing filter, and
 asked you to perform the experiment with your linear polarizing film
If you still refuse to try it out for yourself, then go ahead and send me some film.   I'll repeat some experiments using it on one condition:  that you agree to accept the results.



> #2 If, as you say, the reflection and diffusion inside the softbox polarize the light, then   why do you bother putting polarizing film over it?  The light exiting the softbox would already be polarized.
> 
> Answer
> First its not me saying it, I am only repeating what it says about what causes polarization, that is why I have posted the link to polarization by reflection a half dozen times.
> If you don't like what I am repeating then take it up with the experts.
> Send comments to Wiki prove it to them.
> Because I put my trust into someone who has to stand accountable in front of the science community, and we are not professors in anything.


That is not an answer, it is an evasion.  I'll ask again.  If your expert tells you that your softbox emits light that is already polarized, why do you put a polarizing filter over it.  At best, it would be redundant.  At worst, it would block the light completely.



> Putting Linear polarized film  (LPF) over my soft boxes is the only place you can place it to get a cross polarization.
> If I put the film inside the soft box the defuse panel ( white cloth ) over it.
> It  would create polarized waves to travel at more then just a linear motion.


What motion would it create?  You insist that the polarizing film and the diffuser both polarize light.  Why use both?


----------



## Sylvanite

farmer said:


> #3
> If the air in between the polarizing film and the subject polarize the light, then why did you need to use polarizing film before that?
> 
> My answer
> LOL  didn't we just go through this in question number 2 ?


No.  Question 2 was about "polarization by reflection". This question is about "polarization by scattering".  You said that all light that passes through air is polarized.  If so, why do you need to polarize the light before that?



> # 4
> This is getting weird its the same question asked in three different ways.
> I answered this question 2 questions ago.


No, this question is about reflection off the subject (pen), not reflection within your softbox.  you said that all reflection polarizes light.  If the pen reflection polarizes light, why did you need to polarize the light beforehand?



> #5
> If the air in between the subject and the camera lens polarizes the light, then why doesn't rotating the CPL filter opposite to its axis of polarization block all the light, and turn the image black?
> 
> My answer
> The only way to polarize light between the camera and the subject would be if the light was colliding with something in the air.
> Under those conditions I do not think I will be doing product photography on pens.
> Reason being the only thing I can think of the would polarize the light would be dust .
> And dust and product photography doesn't mix.
> 
> When the suns light finally strikes earth the light has been reflected off of space dust and that is why the suns light is partially polarized and our shy is blue.
> 
> Your talking polarization by scatting out of context ..


Space dust?  Really?  Where on physicsclassroom.com does it say anything about "space dust"?     You said that light was polarized by "colliding with the air", not by colliding with dust.  How is the air in your studio between the light and the subject any different than the air directly between the sun and the object lit it?  Not lit by the sky, but lit by direct sunlight?




> # 6
> If the refraction of the lens elements polarizes the light, then why did you bother using a CPL filter, rather than a plain PL filter on your lens?  Ditto for polarization by scattering of the air between the lens elements and in front of the sensor
> 
> I don't know, your the one who said lenses refract light and creates polarization inside the lens .


No, you are the one who claims that all refraction polarizes light.  See your statements on "polarization by refraction".



> It could be the truth ? my TSE 17mm lens has over a dozen pieces of glass inside.


Ok, if you believe that the elements in your lens polarize light, then why do you bother putting a CPL filter (rather than a PL filter) on your lens.  Wouldn't the "polarization by refraction" create the exact problem that you use a CPL filter to prevent?



> The way understood it the Polarization by refraction laws
> Is the light passes through something like glass then strikes a subject like our pen.


How is the glass before the pen different than the glass after the pen?




> Because of the smooth non metallic surface that is where the reflection or glare is seen.


What about the smooth metallic surfaces of the pen?  Reflection and glare are seen there too.  How do you explain that?  Do you:
Insist that reflection off metal polarizes light, or
Admit that not all reflection polarizes light?
 


> As far as I know humans don't see polarized light until is strikes a smooth non metallic surface like a pen.


Are you saying that polarized light isn't visible?  It is.  The eye sees all light in the visible spectrum -- whether it is polarized or not.  Humans just can't differentiate whether or not light is polarized nor the orientation of polarization (if any).


----------



## Sylvanite

*So what does polarization have to do with pen photography?*

I imagine that most readers are getting pretty tired of following this argument (which I agree has gotten quite tedious) and are wondering what all this esoteric information has to do with actual pen photography.  

Well, I've decided to get the subject back on track.  I'll be making a series of individual posts, each of which will illustrate an aspect of polarization and/or glare with real pen photos.  I hope that they will further people's understanding of lighting, reflection, glare, and polarization in a way that helps them take better pictures.

Before I start, however, let me go over a few basics again.  
*Source light* may be either polarized or unpolarized (photo studio lights produce unpolarized light; filters can be used to polarize it).
*Reflections* can, under some circumstances, polarize light.  Under other circumstances, reflections can depolarize light.  And, some reflections neither polarize nor depolarize light.  Which of these happens depends on the conductivity of the object, its surface texture, and the angle of reflection.  I'll be giving specific examples in future posts.
Physicists may tell you that there is but one law of reflection:  "angle of incidence = angle of reflection", but photographers often divide reflection into two categories:
*Direct reflection* occurs when the surface reflects light solely at the complementary angle (as in the formula above).  Direct reflection may or may not polarize light.
*Diffuse reflection* occurs when the surface scatters or diffuses the light.  That is, the surface texture reflects light at a range of angles beyond the angle of incidence.   Diffuse reflection typically depolarizes light.
Most subjects produce a combination of direct and diffuse reflection, although some can produce one or the other almost exclusively.  Mirrors, for example, produce virtually all direct reflection.  Matte surfaces, such as flat white paint, have a nearly complete diffuse reflection.

Pens typically have a mix of the two types.  Wood grain, for example is primarily diffuse reflection.  A glass-smooth finish, however, will produce direct reflection.  Shiny metallic pen components (nosecones, centerbands, clips, and finials, for example) generally yield direct reflections.  To consistently illuminate pens well, you need to understand how these reflections work and how they interact.  That will determine where you position your lights, what kind of diffusers / reflectors you use, and how you can use polarizers and/or gobos to control glare.


*Glare*, as I have said before, is a strong _direct reflection_ that washes out highlights or otherwise detracts from your pen photo.  Sometimes (depending on the material, glare is polarized, sometimes it is not.


----------



## Sylvanite

*Polarized glare, part 1*

As I said above, sometimes direct reflection will polarize light.  If unpolarized light strikes a non-conductive surface at the correct angle, then the surface can absorb the portion of the light with an axis of polarization perpendicular to its own static charge, and reflect only light with a polarization orientation parallel to the surface charge.  This is what we call a polarized reflection.

Here are a couple of pen photographs exhibiting a polarized reflection.  I deliberately placed the pen and one of the lights to produce a glare line that is polarized.  I put a polarizing filter (CPL) on the camera lens.  Both images are lit the same.  The only difference is the angle at which the polarizing filter was rotated.






In the left photo, the polarizing filter was rotated parallel to the axis of polarization of the glare.  Because they are aligned, the filter transmitted the glare undimmed.  The human eye does not discriminate on polarization, so this is how the pen looked in person.

In the right photo, I rotated the CPL filter 90 degrees.  Now it's polarization axis is perpendicular to that of the glare.  As a result, the filter absorbed all that light - effectively removing almost all of the glare. 

In both photos, the diffuse reflection off the wood, and the direct reflection off the metal components are unpolarized.  Turning the polarizing filter from one orientation to the other did not change the intensity of those reflections.

I hope that makes sense so far,
Eric


----------



## Sylvanite

*Polarized glare, part 2*

A lesser known, less intuitive, but equally effective (if somewhat more expensive) technique is to polarize the light *before* it hits the pen, rather than after it reflects off.  In both of the photos below, I've placed a photographic linear polarizing filter in between the light and the pen (instead of on the camera lens).  You can see it in the upper right corner in each image (and its shadow over the top half of the upper barrel of the pen).






In the picture on the left, I positioned the filter so that its polarizing axis matches that of the glare.  Other than cutting the amount of light reaching the pen barrel, it has little effect.

In the picture on the right, I rotated the filter 90 degrees, so that its axis of polarization is perpendicular to the polarization of the glare.  Just like in my previous post, you can see that the glare in the shadow of the filter has been nearly eliminated.

How does this work?  Well the explanation is very similar to that of a polarizing filter on the lens.   When light strikes the pen barrel at this angle, the portion that is polarized parallel to the surface static charge is reflected (direct reflection) unchanged.  The component with perpendicular polarization is absorbed.  In the left photo, I pre-polarized the light so that there is no light polarized in the direction the surface absorbs.  Therefore, the filter does nothing.  In the right photo, the light is pre-polarized such that there is no light polarized in the axis that gets reflected.  There is no direct reflection because all the light was polarized in the orientation that got absorbed.

The wood of the pen barrel produces diffuse reflection, which depolarizes the light.  It remains visible whether or not the source light was polarized.

The reflections in the clip are also unchanged.  That is because the clip is metallic (conductive).  The direct reflection off the clip neither depolarizes nor repolarizes the source light.  In the above two photos, the clip reflections are polarized in perpendicular directions, but that polarization is not visible in the photo because there was no polarizing filter on the camera lens.  Just like the human eye, the camera's sensor does not discern light's polarity.

I used a small circular polarizing filter in this illustration.  To use this technique effectively in studio photography, one would need a polarizing filter large enough to cover the entire light.  Photo-grade polarizing film is available in sheets of suitable size, but they are more expensive than a typical lens filter.

I hope that was interesting,
Eric


----------



## farmer

*Polarization*

It is a fact  that not all polarized sunglasses are the same.
That's just like CPL and ND filters used in photography ...they are not all of the same quality and its very noticeable in photography...

And the fact is Not everyone who makes sun glasses just  use linear polarized film by its self and some sunglass producers don't use linear polarized film in there ( polarized sunglasses )  .
Why would anyone want to conduct a what is to a very accurate test not use commercial linear polarized film that is what used in photography ?
Apples to apples .......................
When this thread is about the reflection issues in pen photography.

You started this thread teaching members about polarization  ( polarized light and polarized reflection . And what its effects are in photo graphing pens,,,  right ? 
You went into using Linear polarized film and its effects . 
And you have zero experience using linear polarized film in photography.
( what is up with that ) ?
And you seem very negative about using linear polarized film in photography when its used thousands of times every day by professional photographers.
Straight up, how did you come not to like using linear polarized film in photography when you have never tried it once in your life ?

You have disregard or turned a blind eye to polarization by reflection, transmission and scattering. Wiki Links 
You pawned these laws off as well some times you get polarized reflection and some time you dont.
I have never read that !
I believe you twisted or took polarization by refraction out of context.
And what a camera see when using natural sun light, the light is partial polarized and that has been published over and over..
We are talking photography ? and not what the human eye sees .
Because it is also a published fact that humans dont see polarized light like most or like allot of other animals.... and you can include cameras in that list.

Regardless of what you know or you think you know you are not qualified to teach anyone about using linear polarized film in product or commercial photography ......... because you have zero experience .
Because of that and your total disregard to what i would consider the laws of polarization and i do have to thank you because i dont like learning things to debate anyone but I did learn.
4 laws that polarize light........
Polarization by 
Transmission 
Refraction
Reflection 
Scattering.

Where are we, well I have been using linear polarized film in photography  for about two years and i would expect that anyone wanting to teach people about polarization , reflection and glare and linear polarized film would have hands on experience... which you don' or at least not with LPF.

I don't like using using Florescent , can i base my opinion experience  ( yes )
You don't like Cross polarization technic , can you base that opinion from your own experience ???????????   NO 

I like most of your pictures and i think you have allot of experience offering members advise using a light tent and florescent lighting.
I dont know about the rest of your photography skills or technic , but i would guess that you would do a good if not a great job.
But if you have never used linear polarized film in photography at least you should drop your bias opinion.


----------



## Sylvanite

*Unpolarized glare, part 1*

Remember I said that whether or not a direct reflection polarizes light is dependent (in part) on the angle of reflection?  Well, in my posts on "polarized glare", I placed the light at an angle that produced a polarized reflection.

In this post, however, I placed the light at a different angle -- one that produced a glare line, but such that the direct reflection is *not* polarized.  See the four photographs below.  I took them all with a polarizing filter (CPL) on the camera lens, rotated in approximately 45 degree increments.







Unlike my images with polarized glare, rotating the filter had little effect.  The glare line is relatively unchanged in all four photographs.  Even though the blank material (wood and CA glue) is non-conductive, the direct reflection at this angle is *not* polarized, and a polarizing filter does not eliminate it.

So, what can you do to cut unpolarized glare?  Well, there are multiple approaches.  Some of them are more effective than others.  Some are more expensive than others.  Some are simpler than others.  I'll be going over a few of the options in future posts.

I hope that helps,
Eric


----------



## Sylvanite

farmer said:


> It is a fact  that not all polarized sunglasses are the same.
> That's just like CPL and ND filters used in photography ...they are not all of the same quality and its very noticeable in photography...
> 
> And the fact is Not everyone who makes sun glasses just  use linear polarized film by its self and some sunglass producers don't use linear polarized film in there ( polarized sunglasses )  .



So what?  I never said that all polarized sunglasses are the same.  I never said that sunglasses were made from film.  I never said that polarizing sunglasses are of the same optical quality as polarizing film sold for photography.  What I said was that the polarizing sunglasses I used in my demonstration photographs *ARE* linear polarizing filters.  I even posted photographs demonstrating that fact.  I also explained that the sunglasses are just the control for the experiment - not the experiment itself.  If you take them out of the CFL, incandescent, and LED experiments entirely, the results don't change.  Those light sources emit _unpolarized_ light.



> Why would anyone want to conduct a what is to a very accurate test not use commercial linear polarized film that is what used in photography ?
> Apples to apples .......................
> When this thread is about the reflection issues in pen photography.


Linear polarizing filters are linear polarizing filters.  That is an apples-to-apples comparison.  Also, I have posted photos using photographic linear polarizing filters that show the same results.  Do you believe that linear polarizing lens filters are any different than your linear polarizing film?  If so, how?



> You started this thread teaching members about polarization  ( polarized light and polarized reflection . And what its effects are in photo graphing pens,,,  right ?
> You went into using Linear polarized film and its effects .
> And you have zero experience using linear polarized film in photography.
> ( what is up with that ) ?



Again, I never "went into using linear polarized film".  You are twisting my words.  I have only spoken about linear polarization and linear polarizing filters - regardless of their construction.



> And you seem very negative about using linear polarized film in photography when its used thousands of times every day by professional photographers.
> Straight up, how did you come not to like using linear polarized film in photography when you have never tried it once in your life ?



I never said that linear polarizing film doesn't polarize light.  I never said that polarizing filters (on the camera or on the lights) doesn't work.  In fact, I just posted several photographs showing exactly how polarizing filters in either location _can_ (in some circumstances) be used to reduce glare.

What I *HAVE* said is that polarization and cross-polarization are not the *ONLY* tools available to a photographer to reduce glare.  There are other techniques that are equally as effective (and actually more effective) in studio pen photography.



> You have disregard or turned a blind eye to polarization by reflection, transmission and scattering. Wiki Links
> You pawned these laws off as well some times you get polarized reflection and some time you dont.
> I have never read that !



Well then read further.  For example:  "The extent to which polarization occurs is dependent upon the angle at which the light approaches the surface and upon the material that the surface is made of. Metallic surfaces reflect light with a variety of vibrational directions; such reflected light is unpolarized. " - Physics Classroom - Polarization by Reflection - the very same text you yourself have quoted.   It clearly states that polarization by reflection is dependent on:
The angle of the light, and
The material the surface is made of.
That is exactly what I have claimed - and posted photos to demonstrate.



> I believe you twisted or took polarization by refraction out of context.



Of course I did.  You claimed (based on physicsclassroom.com "polarization by refraction") that ALL refraction causes light to become polarized.  I used the exact same source (physicsclassroom.com "rainbow formation") and the exact same misreading (that all refraction causes rainbows) to demonstrate (via Reductio ad absurdum) that your statement is incorrect.



> And what a camera see when using natural sun light, the light is partial polarized and that has been published over and over..
> We are talking photography ? and not what the human eye sees .
> Because it is also a published fact that humans dont see polarized light like most or like allot of other animals.... and you can include cameras in that list.



Published by whom?  Please cite your source.  And *really*?  Are you serious?

If:



farmer said:


> humans dont see polarized light






farmer said:


> I consider all light to be polarized.



Then it must be true that:
Humans don't see all light.
Do you really believe that all humans are blind?  I don't.  By the way this is another example of Reductio ad absurdum.  The logical outcome of your premise(s) is absurd, so it(they) must be untrue.

The human eye sees both polarized and unpolarized light in the visible spectrum - at least, my eyes do.  I'm not an expert on the ocular anatomy of "a lot of other animals", so I can't say whether or not their eyes polarize light.  Are you?  A digital camera's sensor records the light that falls on it - whether polarized or unpolarized - just like the human eye.  Are you really saying that cameras can see polarized glare but humans can't?  Support that claim.



> Regardless of what you know or you think you know you are not qualified to teach anyone about using linear polarized film in product or commercial photography ......... because you have zero experience .
> Because of that and your total disregard to what i would consider the laws of polarization and i do have to thank you because i dont like learning things to debate anyone but I did learn.
> 4 laws that polarize light........
> Polarization by
> Transmission
> Refraction
> Reflection
> Scattering.



Well, I've already said that I'm not trying to teach people how to use "linear polarized film".  Just about polarization in general.  I am about to make a post on "cross-polarization" though, so if I say anything untrue about "linear polarized film" there, I hope someone qualified to teach it tells me.  

I've repeatedly pointed out your many misinterpretations of the physicsclassroom.com tutorials you've reposted.  Most of them come from your misreading the word "CAN" as "ALWAYS DOES", which is incorrect.  I've also pointed out sections you have ignored, such as the one I quoted in red above.

Your statements such as "all light is polarized", and "all light that is reflected is polarized" are in direct contradiction of the very source you quote to support your position.  See the quote above for a specific example.

I am not the one "turning a blind eye".



> Where are we, well I have been using linear polarized film in photography  for about two years and i would expect that anyone wanting to teach people about polarization , reflection and glare and linear polarized film would have hands on experience... which you don' or at least not with LPF.



Again, I never said I have experience with "LPF", nor do I profess to teach it.  I do, however, have experience dealing with polarization, reflection, and glare.  Your wild claims about how everything polarizes light, and all light is polarized have convinced me that although you have been using LPF for two years, and you are getting some very nice results in your photography, you don't really understand why or how.  I encourage you to find someone you trust with some real qualification (not me, and not your misreading of online sources), such as a physicist or a trained professional photographer, tell them that "all light is polarized" and that you have to use photographic polarizing film to repolarize it, and see what he says.

Or, as I've repeatedly requested, you could try these experiments out for yourself.  What better way to test your understanding than by demonstrating it?  If you still refuse, ok.  I give up attempting to convince you to.  You _are_ in good company.  After all, Aristotle used nothing but his common sense and intuition to conclude that heavy objects fall faster than light objects.  That assertion served as the conventional wisdom up until Galileo decided to try it for himself and see.



> I don't like using using Florescent , can i base my opinion experience  ( yes )
> You don't like Cross polarization technic , can you base that opinion from your own experience ???????????   NO


If you don't like fluorescent light, don't use it.  But don't claim that it doesn't work.  Don't claim that it's bad because it causes "polarized electromagnetic waves a.k.a. glare".

I believe that good pen photos can be taken under natural light, incandescent light, fluorescent light, LED light, and strobe light.  I believe good pen photos can be taken with a light tent, with a softbox, and with discreet reflectors and diffusers.  I believe good pen photos can be taken with or without polarizers (film and/or filter).



> I like most of your pictures and i think you have allot of experience offering members advise using a light tent and florescent lighting.
> I dont know about the rest of your photography skills or technic , but i would guess that you would do a good if not a great job.
> But if you have never used linear polarized film in photography at least you should drop your bias opinion.



Thank you for the compliment.  I believe you produce some very nice photos too.  If I seem negative about linear polarized film, it's because I believe that good pen photographs can be taken with much less expensive setups.  I won't tell the members here that they have to go buy a monolight, softbox, and polarizing film/filters when they can (with a little ingenuity) get excellent results with a homemade light tent and a few pieces of cardboard.

My goal is to teach that ingenuity so that people can improve their pen photographs without having to buy thousands of dollars of professional gear.


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## Sylvanite

*Unpolarized glare, part 2:  cross-polarization*

So, if your pen photo composition produces unpolarized glare (as in post #41), and a polarizing filter either before or after the reflection doesn't affect it (as in post #41), what can you do?

Well, there is a technique called "cross-polarization" that can still cut the glare.  The trick is to use two polarizing filters -- one before and one after the reflection.  That is, you put one linear polarizing filter over the light, and another on the camera lens.  The photos below illustrate the effect.  You can see one of the filters at the right edge.  It covers the lower barrel of the pen.  There is another polarizing filter on the camera lens.






In the top image, the two polarizing filters are aligned.  That is, they are rotated so that their axes of polarization are parallel.  You can see that they had no effect on the glare.

In the bottom image, I rotated the filter on the camera lens 90 degrees.  Now the axes of polarization of the two filters are perpendicular.  The glare on the bottom barrel is gone.

*How cross-polarization works:*
Remember I said that the glare (in post #41) was unpolarized?  Well, what that really means is that the angle of direct reflection is one that neither polarizes, nor deploarizes the source light.  Whatever polarization  the source light produces is retained in the direct reflection.  Because the source light (CFL with reflector in this case) is unpolarized, the glare (direct reflection) is too.

Well, by putting a linear polarizing filter over the light in this post, I've changed the pen's illumination (on the lower barrel) from unpolarized to polarized.  The direct reflection (because of the angle) does not depolarize nor reorient it.  Therefore, the glare is now polarized.

Because the direct reflection (glare) is polarized, a polarizing filter on the camera lens can block it out.  When the two filters are oriented perpendicular to each other, the direct reflection is completely removed.

Two notes:
I placed the first linear polarizing filter over the pen's lower barrel but not the upper barrel.  The upper barrel is still illuminated with unpolarized light - which is why the polarizing filter on the lens did not cut the glare when rotated.
The wood of the pen barrels produces diffuse (not direct) reflection.  Because diffuse reflection _does_ depolarize light, the polarizing filter over the light does not change the wood's appearance (other than acting as a neutral density filter).  Again, because the diffuse reflection off the wood is unpolarized, rotating the polarizing filter on the camera lens does not cause that part of the image to darken.

In short, cross-polarization removes unpolarized direct reflection from a photo, but leaves diffuse reflection alone.  

Additionally,  linear polarizing filters act as neutral density filters to unpolarized light.  Therefore, cross-polarization typically requires you to increase the exposure by 2 to 3 f/stops (or a 4 to 8 times longer shutter speed).

I hope that helps,
Eric


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## Sylvanite

*Unpolarized glare, part 3: how cross-polarization fails*

Ok, thus far I've said that 
Glare is a form of direct reflection.
Direct reflection off wood pen barrels can be polarized or unpolarized (or a mix).
Polarized direct reflection can be removed via simple polarization (without affecting diffuse reflection).
Unpolarized direct reflection can be removed via cross-polarization (without affecting diffuse reflection).

And, in post 43, I showed that cross-polarization _is_ an effective technique for reducing or eliminating unpolarized glare on wood pen barrels.

That is not, however, the whole story.  To take the best pen photographs, You need to understand that:
Although glare is a form of direct reflection, it is not the only form.  Direct reflection does not necessarily present as glare.
Pens are made of more than just finished wood.  They usually have at least some polished metal parts.  Polished metal typically produces very little diffuse reflection.  Like mirrors, they primarily yield direct reflection.
If you use cross-polarization to eliminate glare on wood pen parts by removing direct reflection, you'll also eliminate the direct reflection that illuminates the metal pen parts.
Here are a couple of photographs demonstrating that effect.  They show a fountain pen nib lit to show detail on its face.






The top photo was taken without cross-polarization.  In the bottom photo, the nib is cross-polarized.  You can see that the direct reflection off the nib just about disappeared.  If it weren't for some reflection off the background material and a little ambient light in the studio, the nib would have turned completely black.

That is the downfall of cross-polarization in pen photography.  If you use it to eliminate glare on wood or plastic parts, it will also turn your polished metal pen components dark.

Don't lose hope though.  Polarization is not the only means to control glare.  There are ways to light a pen that yield good illumination of wood, plastic, and metal parts and give nice specular highlights without glare.  I'll be getting to them in future posts.

I hope that helps,
Eric


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## Sylvanite

*Eliminating glare by moving lights*

Probably the easiest way to eliminate glare on pen barrels is simply to avoid it outright.  Remember that in post #38 and post #39 I placed a light at a position that would yield polarized glare, and that in post #41 I placed a light such that it would produce unpolarized glare.  Well, in the photo below, I moved the front light (the photos in all four posts were taken with 2 lights) to a location that did not create a glare line at all.






How is this possible?  It's simply a matter of positioning the lights, and angling the pen so that the range of angles that exhibit glare are pointing somewhere other than into the camera lens.  If you are use strobe lights, that task can require some careful thought, or some trial-and-error, but if you have continuous lighting, it's simply a matter of moving things around until the glare disappears.

Yes, it's that simple.  Note, however, that although the pen blank is brightly lit with no harsh glare, the pen hardware is not.  I'll present solutions to that problem in future posts.

I hope that helps,
Eric


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## Sylvanite

*Managing direct reflection part 1:  large light*

So far, you've seen that you can control glare on wood or plastic pen barrels simply by changing the position of your lights.  You may also have noticed, however, that in post 45, there is still glare on the metal parts (the nosecone specifically), and that the metal components are unevenly illuminated (dark patches).  

How do you fix that?  Well the key is to understand that diffuse reflection (as produced by the pen barrels) scatters light across a wide range of angles, but direct reflection (off the metal components) bounces off only at the complementary angle.  Here are a couple of illustrations of how the angles of direct reflection work.  The first diagram depicts a point light source reflecting directly off a curved surface (such as a pen nosecone).






Note that the reflections off different locations go in very different directions.  Now consider how direct reflection off a curved surface affects what a camera sees.






The reflected light that reaches the camera lens comes from widely different original angles.  If you only had one point light source, that spot on the curved surface would be lit, but nothing else would be (just like the photo in post 45).  To fully illuminate the curved surface, you need light coming from a very wide range of angles.

Photographers call this a "large" light.  Here's an example.  I replaced the two 6" diameter lights I used before with a 20"x28" softbox and two reflectors (simply pieces of white mat-board).






The pen is now lit from almost all the way around, either by the softbox, or by reflection off the mat-board.  This is the result.






The barrels are still evenly illuminated (mainly diffuse reflection), and now the clip and nosecone (direct reflection) are as well.  The small dark patch on the clip is reflection from the front, where the camera is.  You can reduce that spot, but you can't eliminate it completely (except by editing the image later).  

There still is a small amount of glare (uneven direct reflection), but that's not necessarily a bad thing.  It helps give the pen a sense of shape and can show off the surface finish.  The glare in this photo is subtle because the direct reflection comes from all around the pen instead of just one angle -- and therefore has much less contrast.

I'll discuss other sources of "large light" and ways to control exactly how much glare you get in a future post.

If this topic is helpful to you, please let me know.  Without any feedback, I can't tell if this thread is useful, or just something taking up lots of my time.

Regards,
Eric


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## Ironwood

Eric, I appreciate the time you are putting into these posts.
The real technical stuff I am just glossing over, as I know I wont retain the info, and if I do need it later I can come back to it.
The last post ( #46 ) I have found helpful as it addresses one of the issues I have been trying to sort out at the moment.
Thank you.


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## rholiday

Eric, very informative, very useful. Thanks, much appreciated!


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## Brian G

Add me to the list of appreciative readers.


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## Sylvanite

*Managing direct reflection part 2: the largest light*

My previous post was about using "large" light.  What exactly makes a light "large" or "small"?  Well, there are two factors:
the physical size of the light relative to the subject, and
the distance between the light and the subject.
Relative to a pen, a 6 inch diameter studio light about 3 feet away is a relatively small light.  A 24 inch softbox 1 foot away is much larger.   With the small light, the pen's direct reflection was uneven and exhibited significant glare.  With the softbox and a couple of reflectors, the direct reflection was even with very little glare.

That does not, however, mean you need to run out and buy a softbox.  I have a couple, but I rarely use them for pen photos.  There are other sources of "large light".

The cheapest one, is an overcast sky.  The sun is physically very large (relative to a pen, anyway), but it is also very far away.  It only illuminates an object from a small range of angles.  Therefore direct sunlight is a small light source.  If the sky is filled with clouds, however, and you're in a open area then that becomes a very large light indeed.   All you need is a few pieces of white cardboard (or even paper) used as reflectors in order for your pen photos to be fully and evenly lit.

I don't have any illustrations for this post - I live in a wooded area and don't have much open sky.  If you do, though, don't be afraid to try it out.

Regards,
Eric


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## Sylvanite

*Managing direct reflection part 3: the light tent*

So far, I've mentioned two sources of "large light".  One is a softbox and reflectors; the other is an overcast sky.  Neither is ideal for pen photography though.  You don't need to go buy expensive photo equipment nor wait for the weather to take nice pen pictures.  Instead, you can buy a simple light tent - or even build one yourself quite cheaply.

A light tent is basically just a box made of translucent white material.  You put your pen in the box, and point your lights at the walls.  The lights illuminate the box, and the box illuminates the pen.  That way, you get a "large" light for more complete direct reflection off the metal pen components.  For a more complete explanation, see http://www.penturners.org/forum/f24/photography-basics-why-use-light-tent-121808/.

A light tent by itself, however, is not a cure-all.  You still need to be careful with the position of your lights.  The most common problem I see with photos taken in tents is putting the lights too close.  Here is an example:  






In the picture above, you can see that I've put the lights right up against the tent walls.  This tends to defeat the purpose of the light tent.  Remember, the idea is make a large light.  When you only light a small spot on the wall, however, you still wind up with small patches of illumination - that is, small lights.  You can see the effect in the pen photo below:






Although this may be a little better lit than with no tent at all, there is still a strong glare line and the pen hardware has large, relatively dark areas.  To fix that, you need to move the lights farther away from the tent.


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## Sylvanite

*Managing direct reflection part 4: the light tent (continued)*

So you've seen what happens if you put your lights too close to your light tent walls.  Now here is an illustration of placing them farther away:






In this demonstration, I've pulled the lights away from the tent.  One is on the left, illuminating the left and rear walls.  The other is on the right, illuminating the right and front walls.  They're pretty far back, casting fairly even light across the entire tent.  

Here is the image that even light all-around produced:






You can see that the pen hardware is nicely lit, and there is no glare off the wood nor metal components.  The image, however, looks a little flat.  Without any specular highlights, it's tough to see the shape of the pen or the quality of the finish.  Remember that I said a little glare is not necessarily a bad thing?  Well, this photo could use some.

One solution is to try to strike a happy medium with light placement.  You can move one of the lights a little closer, so that it lights the entire tent wall, but does so unevenly.  Then the brighter area will yield some shine.  If you have a light tent, go ahead and experiment with light placement to see for yourself.


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## Sylvanite

*Managing direct reflection part 5: the light tent (concluded)*

In my previous post, I said you could vary the distance between the light tent and the lights to control the amount of shine/glare on your pen.  This generally works, but you don't have a lot of control over the shape of the highlight.  In my opinion, straight, well defined edges in the shine look better than an oblong shape.  A simple way to achieve that look is to block some of the light that reaches the tent wall as shown below.











I've taped pieces of mat-board to the light tent to produce a rectangular bright spot on the wall.  Photographers call this a "go-between" or "gobo" for short.  The mat-board controls the shape of the highlight; the distance of the light controls the highlight's brightness.

This is the result:






You can see that the hardware is still nicely lit, but with better definition of the shape.  The wood pen barrel has a highlight that shows off the finish without washing out the detail.  It may not be perfect, but I think it's the best pen photo of this series, and I'd be happy posting it in the Show-Off-Your-Pens forum.  What do you think?

That completes what I planned to say on the topic of polarization and glare, unless anybody has questions or comments.  I hope it helps people improve their pen photography skills.

Regards,
Eric


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## Brian G

Super!  Thank you for showing how placement of lights affects the outcome of the photo.  This is where I struggle, and now I understand why.  Having these photographs of your setup gives me a baseline to start.


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## duncsuss

Excellent tutorial, thanks Eric.


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