Color Correcting Tungsten Lights for Green Screen? In camera? On Lens? Gels? Post?

S

synchroman

Member
Have a question about color correcting Tungsten softbox lights if someone could help me out? I have this JTL Softbox light kit:

http://www.amazon.com/TL-1500-Everlight-Softbox-Quartz-Softboxes/dp/B0000AM6T9/

I want to shoot using these tungsten lights a green screen shot that is supposed to represent daylight. From the reading I have been doing it sounds like I will need some color correction gels? Unfortunately the only gels they seem to sell are 20" x 24" where these JTL softboxes are 24" x 24".

So do I have an alternative to buying gels? Can I do daylight color correction within the camera? (Panasonic GH2). Or maybe just add a filter to the GH2 camera lens? Or can I do the color correction all in post? I am a bit confused as to whether or not buying the gels to color correct the light to daylight temperature is necessary. Can it be done just as easy another way?

I have done some reading around here in the dvxuser.com threads and will continue to look to see if the answer is already out there but so far I haven't found a thead that seems to answer my question.

Thanks all!
 
I don't follow what the purpose of having gels is at all, you should be able to just white balance the camera so that you get a cooler image, which won't cause a loss in light. Doesn't the GH2 let you dial in degrees kelvin?
Also, if you really do want gels, they do sell large rolls of them that will certainly cover those softboxes.
 
Just white balance to the tungsten lights, should work fine. If anything you might want to put a little plus green on the lights lighting the green screen so you can pull a little cleaner key.
 
All video camera are natively setup for 5600 degrees kelvin by using 3200 degrees kelvin lights and color balancing to them you induce grain to the image. This is usually not much of a problem but on green screen the cleaner the image the better. I would suggest CTB for your lights or 5600 degree lights if possible.
 
phudsontx said:
All video camera are natively setup for 5600 degrees kelvin by using 3200 degrees kelvin lights and color balancing to them you induce grain to the image. This is usually not much of a problem but on green screen the cleaner the image the better. I would suggest CTB for your lights or 5600 degree lights if possible.
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If going that route, it would be equally easy to put on an 80a lens filter or something similar....
 
not knowing exactly what kind of daylight situation youre trying to recreate, it would be hard to advise. BUT im not sure id use a budget softbox (or any softbox really) to recreate sunlight on a person. on a budget, id probably suggest something like a lowel pro light with a ctb gel.

as a side note, have you shot green screen before?
 
wgzn said:
not knowing exactly what kind of daylight situation youre trying to recreate, it would be hard to advise. BUT im not sure id use a budget softbox (or any softbox really) to recreate sunlight on a person. on a budget, id probably suggest something like a lowel pro light with a ctb gel.

as a side note, have you shot green screen before?
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I've got a set of Tungsten Cool Lights fresnels and also a JTL softbox set(tungsten) I just assumed the Softbox would create the most even light for the green screen. I'm just doing tests right now. But the end goal is to recreate sunlight outdoors on a sunny day using an actor indoors in front of a green screen.
 
"I want to shoot using these tungsten lights a green screen shot that is supposed to represent daylight."
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This could definitely be problematic. The noise issue and lighting green with a primarily reddish light.

Firstly, you could use different lights for the green screen than for the talent (or gel them green). They should be lit seperately anyway.

The problem with correcting tungsten with 80a filter is that it costs something like 2 stops of light. You need to up the amperage. I bought an 80b filter, which costs less light, but wish sometimes it was the 80c instead. Are you simulating direct sunlight?

Why not just move the operation outside, and use the real thing, or is this supposed to be from a window?
 
Phudson's point regarding in-camera white balance is something I've found to be true; shooting tungsten seems to enhance grain; it can be subtle, but for keying, subtle things can really add up for a tougher key.

I'm in the midst of a massive green screen project; I find 2 of the 2-tube biax flos can evenly light a 9x10 screen. I don't even diffuse them, unless they need to be really close, in which case I might wrap some 1/4 stop around 'em. We're using a screen about 15' wide by 9 high, and I rigged up two holders for those 80-watt flo bulbs, the ones that use a standard household socket, are about 8" long, and have sort of a quad-U-shaped look (Richard used to sell something similar at cool lights). Those 80 watt bulbs are at least a stop brighter than a twin 55w biax fixture. I stick two of those up high and put the biax on each side - very even and bright screen.

Softboxes seem like a bad choice for a decent sized green screen, though I know some folks love them. The inherent softness of flos, and their quick falloff - I find they're great for this. Even some 45 watt spiral photo flos in some clamp lights can work really well - I've used those and taped some white gauzy fabric over the fronts to soften them a hair.
 
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