# Kelvin ratings?



## tlbrooks (Feb 5, 2009)

Hi to all, new guy here. I'm building a photo light tent, (mainly because every place people have recommended buying the kits from are out of stock) I've found some 24 watt cfl bulbs with a 6500K temp rating at a good price. $6.50 for three at the local WallyWorld. Can I make these work ok? I know most people prefer the 5000K but I haven't been able to find them locally. Any thoughts? Thanks for all your help.


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## Tn-Steve (Feb 5, 2009)

Should work with no problem.  There is a good tutorial over in the Library on taking photos, tips on setting the white balance so colors come out right.  That's really what the Kelvin rating is, a measurement of the basic "color" of the light.  (you can also fix that   with programs like PhotoShop, but many folks feel it better if you get it right from the get-go)

One very nice thing about the CFLs is that the lamp hoods/ reflectors don't get hot.  I have a gooseneck lamp on my workbench to help with whatever I'm working on, and I've gotten in the habit of just grabbing the metal reflector and pointing it where ever I need it.  I know that's going to get me one of these days, when I do it with a light with and Incandescent (or worse yet, Halogen) bulb.

Hope this helps,

Steve


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## gketell (Feb 5, 2009)

5500K is the color of light on a "sunny day".  6500K is a "cloudy day".  So you can either adjust in camera by setting your camera to "shade" or "cloud" light, or you can use a grey card and get perfect color in software.  I recommend the latter but it depends on how much time you want to spend editing vs turning and just how picky you want to be about your photos.  If you are selling via the photos you should be very picky.  If just for entertainment you don't need to be as picky.

GK


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## Art Fuldodger (Feb 5, 2009)

I wouldn't use them.  Fluorescent lights don't have a continuous spectrum, but spikes in the spectrum to simulate a certain temperature.  In fact, they kind of have to fudge in order to even give them a color temperature at all, as they don't match any black-body radiator.

Color temperature is only important in that you have to adjust for it somewhere in the process, but doesn't have nearly as large of an impact on the quality of your color as does CRI, or Color Rendition Index.  There are some fluorescents with decent CRIs, but they're not cheap, certainly not 3 for $6.50.  You can also buy incandescent lamps made to have a somewhat precise color temperature and extra-high CRI, but they're expensive, and are only guaranteed like that for a surprisingly few number of hours.

The cheapest way to go in order to get copious quantities of decent-spectrum light is to use halogen worklights.  You can pick up a 250-watt halogen light at Home Depot for a little less than $5, and 500-watt units aren't much more.   Heat is a concern if you have wax finishes, but you don't have to leave the pen in there all day.

If you're on the cheap and still want to try it with lower light levels, Ikea has a "scratch and dent" section, and I see small halogen (GU10/MR16/MR11) lamps going for a few bucks there quite often.

It's also possible to do strobes fairly cheaply, as you can get small slave flashes (optical slave, too) for around $20 each, with guide numbers up to 50.  But depending on your camera, it may or may not be a simple thing to get them to fire without the camera's TTL metering pre-flash making them fire early.


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## Neal Addy (Feb 5, 2009)

6500 is kinda warm but you might be able to make it work.

What camera are you using and how comfortable are you with Photoshop?


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## pipecrafter (Feb 5, 2009)

Personally, I use Sylvania 23W 6500K CFL bulbs in my photo setup.  As long as I set the custom white balance (by shooting a white background) in my camera, it is perfectly faithful to the actual colors.  Sometimes using automatic white balance works okay as well.  

And the key is being able to set the custom white balance.  6500K CFLs *do* cool down the colors, so being able to counter that with a custom white balance is necessary.

I do not like halogen lamps.  One, they consume far too much electricity for my liking.  But they also tend to warm up the image a lot - again, requiring a custom white balance setting.  I have found, over the last several years of taking photos in a light tent, that countering cool light is far easier than countering warm light.  Also, I've had it beaten into my head by my mother the artist, that cool northern light is the absolute prefered natural light for painting - so I try to get as close to that for my pictures as I can.


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## Art Fuldodger (Feb 5, 2009)

pipecrafter said:


> I have found, over the last several years of taking photos in a light tent, that countering cool light is far easier than countering warm light.



  In my experience, the continuity of the spectrum is what has always determined how easy it is to get the color, adjusting for a higher or lower color temp is much easier.  There are more reasons than one why professional photographers rarely (if EVER) use fluorescent lights...

As for the halogen lights taking too much electricity... how long do you need to leave them on to take a picture?


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## tlbrooks (Feb 6, 2009)

I was able to find some of the 5500K made by E.luminate (??) seem to work fine. About 4 bucks apiece. I'm using a Canon A640 10MP point-and-shoot camera. It has some nice features including the ability to adjust white balance and play with different color settings. I'm finishing up my homemade light box tonight and I'll be able to play around with it over the weekend. We'll see how everything works out.


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## pipecrafter (Feb 6, 2009)

Art Fuldodger said:


> In my experience, the continuity of the spectrum is what has always determined how easy it is to get the color, adjusting for a higher or lower color temp is much easier.  There are more reasons than one why professional photographers rarely (if EVER) use fluorescent lights...



Well, since I'm not a professional photographer, I guess good enough is good enough.  Frankly, I've never had a problem duplicating colors.  Combating the Curse Of The Shiny, yes - colors, no.  Now, mind you, this is a system built up over several years of trying to duplicate colors very faithfully (important for what I make).  I won't claim to be an expert in photography, but I know what works for me - YMMV.



> As for the halogen lights taking too much electricity... how long do you need to leave them on to take a picture?



Actually, I leave them on for quite some time.  I do marathon sessions of photography that can last for an afternoon.  Sometimes what looks good in the viewfinder doesn't look so hot once it's displayed the computer, and I go back and take more photos.

Besides, using less electricity is never a bad thing.  Admittedly, I may take that to an extreme - but hey, it is what it is.


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