# Photoshop Tip #4 - Dynamic Range



## Sylvanite (Mar 27, 2011)

There are several problems with getting a photograph to look good on the Web.  One of the big ones is that no two monitors look exactly the same.  I regularly use three separate displays and pictures appear distinctly different on each.  One has good color rendition and contrast.  Another always looks a bit oversaturated.  The third (and the one I use most often) is a little dull and dark.  There's no way to make a photo that looks its best on all three.  Even if all monitors were the same, the way we perceive colors changes with ambient light.  I've even noticed that I see colors slightly differently in each eye.  

Therefore, it's simply not worth trying to get a web photo perfect.  The best that we can do is shoot for an image that looks good to the widest possible audience.  This tip contains the simplest mechanism I've found for standardizing a photo for that purpose.

I'm going to start, however, with a seemingly different discussion - exposure and lighting.  Here are three different shots of the same pen.  One is slightly overexposed, one a little underexposed, and one correct.



Notice in the first photo that the highlights are a little blown out.  The second one looks dark, or "muddy".  The third is correctly exposed, but is a little lacking in dynamic range.  That is, the whites aren't totally white, and the blacks aren't completely black.  Such a photo could be characterized as "dull".  I see this problem most often with insufficient light, or when using a light tent.  When we diffuse light to cut harsh shadows, we often rob the photo of dynamic range as well.

If you have trouble judging correct exposure just by looking, you can load the photograph in Photoshop (I'm using Photoshop Elements version 8 in this example), and click "Enhance -> Adjust Lighting -> Levels"


This will bring up a histogram (which is a graph that shows how much of a photo is how bright).  Assuming an even tonal balance in the subject, an underexposed photo's histogram will show lots of dark, and little to no light areas.  An overexposed photo will show a spike on the far right with little to the left.  The histogram for a correct exposure will not have gaps on either end, or at least the gaps will be even.


High values on both ends of indicates that the subject has higher dynamic range than the camera could capture. Gaps at the ends is a sign of low dynamic range.  It means that the photo has middle tones, but lacks extreme dark and light areas.  There are ways of handling excessive dynamic range by merging multiple photos, but I rarely see that problem in pen photography.  Low dynamic range is far more common.

The solution is very simple.  In the Levels dialog, click <Auto>.  Photoshop will expand the range of each color channel, yielding brighter highlights and darker shadows, without losing the detail in either.  This almost always produces an image that is more lively, and will display better on a wider variety of monitors.  If you like the result, click <OK>.  If not, click <Cancel> or <Reset>.  You can also adjust the sliders, or input values for greater or lesser effects.  The same effect can be achieved from the main menu by clicking "Enhance -> Auto Levels".  Here is the result:


"Auto Levels" is typically one of the first adjustments I do on a photograph.

I hope that helps,
Eric


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## MartinPens (Mar 27, 2011)

Two key components for consistently accurate photos (although the whole monitor thing is true) is to meter the light at the subject (I use the ExpoDisc to keep that step simple) and spend a few bucks to calibrate your monitor. (I use the Spider3) Of course, I'm a graphic design geek and have always had to calibrate my monitor. It eliminates much of the frustration of taking a photo (with an incorrect light balance), loading on the computer (with an off color uncalibrated monitor) and trying to get the colors to look like you saw them.  Get a decently lit photo to begin with and just upload, sharpen slightly and post. Most cameras nowadays take a decent photo in proper light.

Thanks for the tips. I hope you get some good feedback for those who are being helped by them. I enjoy them.

Martin

Sent from my iPad using Forum Runner


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## soligen (Mar 27, 2011)

I dont see an auto feature in GIMP that does a decent job, but I think I'm getting the same effect using Curves.  With your explanation of dynamic range, I better understand GIMP Curves and now realize I can do a lot more with it than I thought. 

Thanks!


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## Sylvanite (Mar 27, 2011)

MartinPens said:


> Two key components for consistently accurate photos (although the whole monitor thing is true) is to meter the light at the subject (I use the ExpoDisc to keep that step simple) and spend a few bucks to calibrate your monitor. (I use the Spider3)


I used to calibrate my monitor with a "huey", which not only adjusted video settings, but also had an ambient light sensor and would change display colors throughout the day as room light changed.  It still didn't make the printer match the monitor, which is what most photographers care about.

No amount of fiddling, however, could get my monitors to match.  The laptop screen simply isn't bright or contrasty enough.  My big display was made by a tv company and I just can't get it desaturated no matter what I do.  The other monitor is actually quite good, just in an inconvenient location.  So, I depend on Photoshop over my display sometimes.



> Get a decently lit photo to begin with and just upload, sharpen slightly and post. Most cameras nowadays take a decent photo in proper light.


Absolutely.  The better job you do in camera, the less you'll have to do later.  "Decently lit" is the difficult part, though.

Regards,
Eric


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## Sylvanite (Mar 27, 2011)

soligen said:


> I dont see an auto feature in GIMP that does a decent job, but I think I'm getting the same effect using Curves.


Curves allow detailed tonal control across the entire brightness range of each color channel.  You can create a complete color profile with curves to correct for sensor response and monitor differences.  Curves are difficult to use effectively, however, if you don't have a good understanding of what they do.  You're doing really well if you can manipulate curves successfully.

It might be easier to use the levels sliders to set the black, white, and gray points.

Regards,
Eric


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## 76winger (Mar 27, 2011)

Thanks for the tips Eric. I'm always looking for ways to create better photographs of my pens.


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## moke (Mar 28, 2011)

Hey guys I have been using X-rite Eye One Display 2 calibration tool. I just changed from the Spider about 6 months ago....not sure I like it. Have any of you got any experience with X-rite? I am calibrating a Lacie monitor, and have to make some "adjustments" from recommendation to achieve correct calibation!


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## Geppetto (Apr 15, 2011)

If you're going to do post processing on your images, you should consider using the RAW format on the camera.  The RAW format increases your ability to manipulate an image by orders of magnitude. Think of a RAW image as a digital negative.  Your computer then becomes the darkroom.  

When you save a shot in JPG, the camera processes the image and then compresses it, loosing valuable data as part of the operation.  When you save a shot in RAW,  it is saved exactly as the sensor recorded it, without loss of data so that you can later process it on your much more powerful home computer or laptop.   

 For example JPG stores 8 bits of information per color channel (millions of colors).  Raw stores 12 to 14 bits of color information per channel (billions of colors).   When you're making a color adjustment on your computer,  you have a significantly greater depth of colors with which to make the adjustment on a RAW image vs. a JPG image.  The story is similar for white balance, exposure and contrast etc.     

 The down side of the RAW format is that it takes much more storage space and it takes longer to save them than JPG files.     

You also need to process the RAW files differently.   Photoshop has the functionality built in where as GIMP requires a UFRaw plug-in.   The basic controls for RAW are quite similar to the controls for the 8 bit images, it's just that you have a much broader range of adjustment within those basic controls.  After the RAW processing is complete, then you can save the superior image in JPG and apply any special effects or other manipulations as you normally would.  

 This all sounds more difficult than it is.  I just have a bad case of geek speak today.


 Sherri


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## wb7whi (Apr 16, 2011)

Raw is only available in the higher end cameras and I suspect that many here are using point 'N shoot cameras so a photo editor becomes more important in post production editing.

Wayne

Wayne


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