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Is color temp of green screen lights critical?

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Bob Cole
Is color temp of green screen lights critical?
on Dec 19, 2016 at 10:48:36 pm

Sort of an academic question, but it may come in handy some day when I'm shorthanded with lighting: how critical is the matching of the color temp of the key and green screen light?

What made me wonder about this was seeing green Kino tubes. I've never used green Kino's to light a green screen; when you do that, does the color temp of the keylight matter? If not, why not? Does green-lighting a green screen somehow free you up to use whatever color keylight you want?

I've always matched the color temp of the lights on the green screen with the lights hitting the subject. Tungsten/tungsten or daylight/daylight. Is that necessary? I have never made the mixed lighting experiment, and I wonder whether anyone else here has.

Bob C


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Todd Terry
Re: Is color temp of green screen lights critical?
on Dec 19, 2016 at 11:10:19 pm

Hey Bob...

You'll probably get some purists here who will contradict me (and I will humbly bow to their wisdom), but for me personally and in practical experience I've never bothered one bit to worry about matching the color temp source of my greenscreen lighting to those of the key. In fact, I will often mix them.

In theory it shouldn't matter at all, if a green surface is hit with light, it is going to only refect the green part of the spectrum, no matter if it is getting hit with 5600° or 3200° or something in between... with the rest of the spectrum being absorbed. That's in theory... in practicality it doesn't work quite that way, if you blast a greenscreen with a tungsten source and then with a daylight source you will see a bit of a difference to your eyeball... but I've always found it to be completely in tolerance with what is compositable and never had any matting problems.

But because there is a little bit of a difference in how the two sources are photographed, I wouldn't mix them on the greenscreen just for the sake of uniformity... I'd try to light the green solely with one type or another, not daylight in one area and tungsten in another. But in relation to what you are using to light your subject, I don't think it matters at all.

I have two big 4' flos that I use vertically for greenscreen lighting. I have daylight tubes for them, as well as tungsten tubes. Honestly I never even check when I'm setting up for greenscreening, I use whatever is already loaded in there, because I've never found it to make a difference. The last time I did this (a couple of weeks ago), they were actually half-n-half (each instrument had half daylight tubes and half tungsten). And it was just fine to mix them.

I think the only real thing to worry about is the rare instance (and it does happen now and then) where your greenscreen instruments spill a bit (either accidently or on purpose) and also directly hit your subject... maybe a little splash on the edge of a subject, etc. In those rare instances you'd likely want to make your sources match... but as long as it is purely reflected light, put me in the "It doesn't matter" category.

Others may disagree, will be interested to hear....

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com



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Erik Anschicks
Re: Is color temp of green screen lights critical?
on Dec 21, 2016 at 5:19:55 am

Another vote for "It doesn't matter." Like Todd said, I am sure there might be SOME reasons people give for doing this and they might well be right....but I've lit greenscreens with many different instruments and colors temp mixtures over the years and have never once noticed a problem at all, nor had one reported back to me.

I guess in theory, deeper green hues MIGHT make for a cleaner key in some circumstances, but it's certainly not enough of an issue that I'd worry much about it.


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Bob Cole
Re: Is color temp of green screen lights critical?
on Dec 21, 2016 at 9:46:12 am

Thanks, Todd and Erik. I'm transitioning to bi-color LEDs, but to light the chroma key evenly, I like to place the green screen lights as far off as I can. Knowing I don't have to worry a bit about matching the key and the green screen lights means I can use my old, powerful tungsten broads for that. And that's going to save me some... green.

Thanks again, and Merry Christmas!

Bob C


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