Green Screen Light sizes

[Dennis Size]

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

[Bill Davis]

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.

[Charles Mercer]

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