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Green Screen Light sizes

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Zvi Twersky
Green Screen Light sizes
on Dec 31, 2009 at 12:56:47 pm

We need to get lights for our green screen room. Everywhere I look, I just see the importance of even light on the green screen but now that I need to buy them, I'm a little stuck on the light sizes and maybe someone can help me with the light sizes. (Not the key or fill light - just for the walls)

The cyc we have is 3 walls that need to be lit (lights will be hung on ceiling). The back wall is about 77 square feet and the side walls are about 90 square feet.

I would assume we need 3 lights for the ceiling, one pointing towards each wall. Can someone tell me if this is correct and what sizes the lights should be to cover the walls? (size, watts, whatever will explain it)

Thanks.





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Mark Suszko
Re: Green Screen Light sizes
on Dec 31, 2009 at 2:07:22 pm

There's different ways to do this, more than one can work. Long tube fluoros can be arranged in a frame along the edges of the wall and ceiling to wash the wall for head-on shots. Or banks of soft light boxes, which I prefer, which make a very even lighting over a wide area, but these take up lots of space and may not fit your little alcove.

I think the hardest way to light green walls is with spotlights, unless you have a LOT of them; it is challenging to get truly even coverage. And your room will get HOT if you use a lot of them for long. Your electric grid will pull lots too. But the compact way to light your wall may be an overhead grid of fresnels doing that.

If it was me, for simple single-man stand-ups, I would use a couple of Lowel's largest-sized Rifalights pointed into the back wall from the sides, one left, one right, then a separate lighting setup on the talent, standing at least six feet forward of the back wall.


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Dennis Size
Re: Green Screen Light sizes
on Jan 2, 2010 at 12:44:27 am

Please list the width and height of your greenscreen walls.
You will need to hang your fixtures from the ceiling, about 3'-0" away from the walls. My rough guess -- without knowing exact dimensions of either your walls or your ceiling height -- would be six 2 lamp x 4'-0" Kino Flos (two lighting each wall)..... or three 2 lamp x 8'-0" Kino Flos (one lighting each wall).
You could also get away with three 2 lamp x 2'-0" Kino Flos on each wall. My preference is always to hang fewer instruments however.

This would be the correct way to go. If you choose not to purchase the rather expensive (but foolproof) Kinos there are many other choices, such as cyc lights, scoops, mini-10 wash lights, etc.

DS





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Mark Suszko
Re: Green Screen Light sizes
on Jan 2, 2010 at 6:49:40 am

Denis is absolutely right.

OTOH, if you use the Rifas, they can also go on location to be used for other things, like shooting field interviews, the strip/cyc light is a one-trick pony. Don't know if that makes a difference.


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Zvi Twersky
Re: Green Screen Light sizes
on Jan 2, 2010 at 11:48:36 am


Height of walls (from raised stage to ceiling) are about 2.15 meters\7 feet

Width of left and right wall are about 3 meters\9.8 feet

Width of back wall is about 4 meters\13 feet

Does your reply apply to these measurements?

Thanks



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Dennis Size
Re: Green Screen Light sizes
on Jan 4, 2010 at 4:35:05 am

If you want to use KINO FLO fluorescents -- which would be the easiest and best way to go -- you can use 3 single tube x 8'-0" Kino Flos (one for each side); or 6 single tube x 4'-0" Kino Flos (two for each side).
If you don't have the money. You could also use about twelve evenly spaced 10" tungsten scoops or single cell cyc lights.

DS



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Zvi Twersky
Re: Green Screen Light sizes
on Jan 4, 2010 at 7:18:47 am

I used your replies and went shopping yesterday with my boss yesterday. It seems he is going to go with Kino. On Tuesday one of the places are sending a light technician, free of charge, to advise us on all the lighting needs at the place. I will keep you posted.

Once again, thanks to you all.



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Dennis Size
Re: Green Screen Light sizes
on Jan 4, 2010 at 7:30:23 am

Hmmm... a vendor is sending a lighting technician to tell you what you need to buy from THEIR store?
Let us know what you end up with.

Remember also ...with Greenscreen .... less is better than more.

DS



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Zvi Twersky
Re: Green Screen Light sizes
on Jan 4, 2010 at 8:15:35 am

We didn't go to stores but manufactures. The place that are sending people is a huge complex bigger then a home depot with a ware house that has every type of light system you can imagine. They showed us around for about 30 minutes and I showed them pictures of the room and they were very professional. The visit and advice is with no strings attached. They pretty much told me the same things you guys wrote here so it seemed like they knew what they were saying.

They also provide lighting systems for all the main TV stations here.



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Charles Mercer
Re: Green Screen Light sizes
on Jan 6, 2010 at 9:33:38 am

I'm in exactly the same positon with the green-screen lighting, although my set-up will be smaller - just an eight feet wide heavy green cloth. I've used this successfully in my living room draped over the curtain pole (Yeah, I know!) but now it's going into our new studio. We light our talent on location with a Rifa66 and combination Arris for the trad three light arrangement. I'm going to go with fluorescent strips on stands for the green-screen lights - two should do the job I think. We'll use the same talent arrangement in the studio. But here's a question - I'll use 3.6k tubes to match the talent lights, but if you use daylight rated tubes on the screen, does this make a difference to the colour temperature of the green-screen? Or does Final Cut simply see this as a green colour, no matter what lamps are used?

Regards

Charles

Charles Mercer
Pearldrop Video Productions


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adam taylor
Re: Green Screen Light sizes
on Jan 6, 2010 at 11:48:05 am

Unless your lighting for the green screen spills onto the talent, i don't see you having a problem with a lighting mix. Ideally your talent lighting should be unaffected by the green screen lighting - no spill either way.

FCP and every other video keyer allows you to sample the green directly from the video, so it can work out exactly what shade of green you want to key.

However, having only type of lighting could be more practical when it comes to replacing blown lamps, etc.

Adam Taylor
Video Editor/Audio Mixer/ Compositor/Motion GFX/Barista
Character Options Ltd
Oldham, UK

http://www.sculptedbliss.co.uk


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Charles Mercer
Re: Green Screen Light sizes
on Jan 8, 2010 at 9:03:41 am

Thanks for the info. The problem is cost - I know I could buy fluors tungsten rated tubes - Kino etc - but I need two instruments and the cost is going to be prohibitive as we are starting up. I'm tempted to use ebay and buy a kit of three softboxes with switchable fluorescent bulbs. These are rated at a total 2750 watts (equivalent tungsten) and will keep down both heat output and power consumption. I like the idea of being able to switch off lamps as this will give us a lot of control. The only problem I can see is replacement lamps as the supplier doesn't list them, but I've emailed for enlightenment on this point.It seems to me if there is a colour temperature problem between the talent tungsten and the green-screen daylight temperatures, I could always gel the screen to lamps to balance the light.

Regards
Charles

Charles Mercer
Pearldrop Video Productions


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Dennis Size
Re: Green Screen Light sizes
on Jan 6, 2010 at 9:17:05 pm

You'll be fine, although your fluoros are easy enough to color correct.
The only concern will be color corruption on your talent. Make sure your green screen fluoro wash isn't lighting them. As it is, the 3000K talent lighting will be polluting the color of the green screen.

DS



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Bill Davis
Re: Green Screen Light sizes
on Jan 6, 2010 at 11:23:38 pm

Warning, DANGER.

You say the back wall height is just 7' from Stage to ceiling???

That's gonna provide you BIG problems in getting even light on a front lit greenscreen.

You'll need to get your insturments OUT from the wall to have any hope of evenly lighting the GS - and with only 7" of ceiling height, a regular human standing upstage is going to cast shadows on the screen.

Think of it this way. If the GS light is positioned at the top of the 7" wall but just a few inches out from the wall - then you've got VERY bright green fading to VERY dim green top to bottom. That's a horribly uneven light field with massive drop off at the center of the screen. You'd LIKE to see a nice right triangle - best would be a right triangle with the vertical leg equalling the horizontal leg. So the light would be 7 ft out from the ceiling/wall - or floor/wall dimension. But think of how that's gonna screw up shadows cast by anyone on stage. You can cut your distance out from the wall in half, to 3.5 foot. but then the lower wall key will suffer from inverse/square falloff. So you can try doubling your lights to have one from the ceiling mirrored by one footlight and you'll probably be OK. But again, you need at LEAST that 3.5 feet out from the back wall totally clear.

But while that will give you pretty good key lighting, it's still gonna wreak havoc on your shooting angles because that's just a WAY compromised height for a standing subject.

In my studio, I fight and fight with the fact that I only have 11 feet of overhead clearance - and in a lot of setups, I have to raise the camera and shoot moderately down from the talent eyeline if I want to do head to toe GS work.

In your situation, I'd be thinking a whole nother approach. Possibly a background wall of many fluor tubes - with significant diffusion over them - perhaps those plastic prismatic ceiling tile light diffusion lenses - to spread the tube highlighs evenly over the lit surface, then a translucent key green fabric over that.

Unless I'm understanding this wrong your camera angles will constantly be losing key at the head or floor of nearly all shots. And the further back you move your cameras to take full stage shots, the worse your problem with cut-off key heads and feet will be.

My 2 cents anyway.



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