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Old October 30th, 2002, 10:40 AM   #1
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Gels - Color - White Balance

Is there a visible difference in hue between tungsten, incandescent, halogen, and fluorescent lights when they are all covered with blue gels? And how would white balance affect a scene lit only with blue-gelled lights?

And for a real mind-bender...if one accent white light is halogen...and you set the white balance based on it, then dimly light the rest of the scene with blue-gelled lights...does it matter if the blue-gelled lights aren't halogen?
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Old October 30th, 2002, 06:28 PM   #2
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The change in hue is measurable and visible. But the question is, is it significant? There are so many variables in your question it is impossible to give a definitive answer.

A blue gel will change color temperature a certain number of degrees kelvin. Use the color temperature of the source light and add the factor for the blue gels. The change can be measured with a color temperature meter. In most situations the human eye will probably notice a color change from various source lights. But will it be significant? Probably not.

Depending on the camera and the color temperature of the light sources, white balance will correct for the blue light sources. If you want white paper to look white (rather than blue) white balance under your lighting conditions. The white balance will correct (to the best of the cameras abilities) for the color of the source lights and make whites appear white. The other colors (skin tones etc.) will fall into range too.

Remember, the white balance is always trying to make whites look white. It always assumes that what you are using to white balance to, is white. Here's where the fun comes in. If you are using blue gels to make a scene look blue, do you really want to white balance? White balancing will negate the effect (to some degree) the effect of the blue gels. If you want to accentuate the effect of the blue use a warm color (instead of white) to do the white balance. By choosing a warm color (yellow, orange, red) the camera will actually add blue to the color balance of the scene. Sounds like fun, huh.

You can actually make your own custom white balance cards by printing out various shades on a photo quality ink jet printer.

In answer to your last question, it depends on if you need or even want consistent color lighting. Walk into a dimly lit room and let your eyes adjust. The local colors will start to become apparent. The colors of drapes, carpet, walls and furniture all tint or affect the areas around them. Are you after consistency or realism?

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Old November 3rd, 2002, 03:45 AM   #3
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Thanks for the thorough answer, Jeff.

I planned on white balancing based on the one white light in the room, which will either be halogen or fluorescent. As far as the blue-gelled lights go...it'll be just whatever I can scrounge up and assemble. I like the idea of white balancing with a warm card since I'd like the white light to have a "cool" slightly blue hue.

I recently saw a trailer on the Quicktime trailer site for the movie "They." The lighting in the bedroom scene (after the lamps are turned off leaving just the moonlight) is almost identical to what I'd planned to do.

I'll do some tests soon and let you know how they turn out.
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Old November 3rd, 2002, 07:26 PM   #4
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I have a follow-up question...

I went shopping around Tokyo yesterday for blue gels and surprisingly only found a couple of stores that have anything in stock, and they looked to be identical in density and hue.

So, looks like I'll have to order...and that produces a quandary. What do I order? In looking at the

http://www.cavision.com/Lighting%20G...r_effeicts.htm

page, I see there are several different blues listed...
  • 061 - Mist Blue - Night scenes, cool wash
  • 063 - Pale Blue - Cycloramas, cool wash
  • 068 - Sky Blue - Night effect, Cycloramas
  • 071 - Tokyo Blue - Deep blue, midnight scenes, Cycloramas, skin tones
  • 075 - Evening Blue - Good for night scenes, romantic moonlight
  • 079 - Just Blue - Cycloramas
  • 085 - Deeper Blue - Moonlight, strong backlighting
...but I don't have a clue which to order! Any suggestions?

The blue I'm looking for will be moonlight pouring in through a bedroom window at night, light enough to illuminate the subject, but "blue" enough to put the focus on some bright white light spilling in through a cracked door.

Thanks for any advice.

P.S. Cyclorama?! What's a cyclorama?
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Old November 3rd, 2002, 08:19 PM   #5
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Check out Rosco http://www.rosco-ca.com/intl/products.html If you can't find them in video supply houses try theatrical supplies.

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Old November 3rd, 2002, 08:35 PM   #6
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Cycloramas can be either hard (constructed out of plywood, sheet rock, plaster) or soft (fabric). They are used on sets for large products (cars) or TV sets (backgrounds). Sometimes they are painted or lit with gels. They are used a lot in ultimatte work. They sweep into the floor and if lit properly no shadows or hardline where the floor and wall meets. Hard to describe. They are sometimes painted to look like the sky or can be used to project an image on. This might also help http://www.miamifilm.com/CotechFilters1.html

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Old November 3rd, 2002, 08:38 PM   #7
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<<If you can't find them in video supply houses try theatrical supplies.>>

Man! I wish life here were that easy, Jeff! In most cases, it takes so long to get a native-speaker to help you find a place listed online or in the yellow pages, then to actually find the place...then when you get there, to find they either don't have what you need, or if they do it's 2, 3, or even 4 times the U.S. price... it's usually better to just order online from overseas. The shipping and customs tax you pay is still usually far below the retail price...and you've saved a couple of hours of your life in the process.

The Rosco link also has a lot of blues listed...but again, I'm not sure which is best for my needs.

Thanks for the info about cycloramas. I'm an old still photographer...and what you've just described I simply called a background. ;) I'm bad about bypassing terminology...or creating my own sometimes.

Too bad Cavision and Rosco don't have stills showing the effect of each of their gels.
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Old November 3rd, 2002, 09:06 PM   #8
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By the way, in searching the web for some still shots showing blue gel examples, I found this page on three-point lighting. Pretty interesting.

http://www.film-and-video.com/broadc...les3point.html

The search for blue gel examples continues...
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Old November 3rd, 2002, 11:55 PM   #9
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John,
Here's one more resource that you might find useful. I've ordered all of my gels and related stuff from Studio Depot

https://www.studiodepot.com/store/index.cgi

It's actually Mole-Richardson's retail outlet.
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