Greenscreen

K

kakfilm

Member
I'm trying to light a green screen wall and encountered a problem that I've never encountered before. I always get a hot spot every time I try to light it. I've tried using different lights from soft box to flood and I still get the hot spot. Anybody know what I'm doing wrong? I've even tried dimming the lights down and it's still there. I'm beginning to think it's the wall, but I'm not sure. Any advice, suggestions?

Kak Lee
www.myspace.com/kaklee
 
You didn't tell us much about how many fixtures you're using and that could be the key if you're using just one. You can't use just one light normally to light the screen especially if the needed area will be large. Secondly, you might try fluorescent shop lights or kitchen ceiling 4 foot fluorescent fixtures with electronic ballasts from Home Depot or Lowes. You may need 4 fixtures to do it well. Next, you'll light in 2 layers. One layer for the screen itself and another for the subject. Don't try to do it all with the same fixtures as that just doesn't work all that well. Make sure the screen is lit evenly with as many as 4 fixtures (1 from each side facing in at 45 degrees and if possible, another 1 or 2 from above shining down at 45 degree angle also). Then using whatever is appropriate to light the subject, set that up in front and have as much separation between the subject area and the screen area as possible to keep shadows from subject falling on screen and green spill on subject from being a problem.
 
I started with a cyc light just to see how the green screen was going to look like and spoted the hot spot. I then put a diffuser in front of it and the spot was still there. I then added two more diffused lights to it and the two new lights added two more hot spots. I then added two more and it just keeps adding hot spots. I tried different diffusions and frost and the hot spot wouldn't go away. That was when I took out the soft box and lit with it and it was still there.

I've lit a green wall before with a whole band in front of it and there was never a hot spot anywhere. In this setup I lit the wall with only two soft box and I light the bad with fresnels. I got a pretty good separation out of them.

I've pretty much tried every trick I can think of with this new set up. The only reason I thought it might be the wall is because this is a brand new studio that was put up by home construction people who's never done anything like this before.

Any more advice and/or suggestions would be appreciated. Thanks in advance.

Kak Lee
www.myspace.com/kaklee
 
1. Surface - diffuse
2. Paint - Rosco Green DigiComp Paint.

OR (Use a professional fabric green screen material)

3. Kino Flo style lighting. (always in pairs) above and back from surface a minimum of 6 feet. Angled 45 degrees down. (If using stand based from either side 45 degrees in as well)

If you are getting hot spots from kino flo style lights then your lights are too close to the screen.

Separation from back of screen lights to start of talent should be about another 6 feet. This is minimum to allow proper backlighting of talent and minimum spill. Then set key and fill on talent normally.
 
I'll bet they used glossy paint on the greenscreen area. That's a definite no-no and may be what is causing your problem.
 
I know the paint is not glossy. It's flat. Are there different levels of flat paint? I do not think the paint is chroma key paint either. It's colored green, but I think it's just regular flat paint. Could this be the problem?

Kak Lee
www.myspace.com/kaklee
 
Perhaps could be the problem. There are indeed different levels of paint. You've got (at least) flat, satin and glossy and there may be others. If it was the satin which is sort of between flat and glossy, I think you could have some issues. Its hard to imagine what else may be getting you other than the paint. What about the walls themselves? Do they have texture on them or just smooth sheetrock?
 
I just looked at our paint and it is latex flat. All of the chroma key paint I've seen online are acrylic. I'm guessing this might have something to do with it? What's the different between latex and acrylic?

Kak Lee
www.myspace.com/kaklee
 
I doubt the difference between latex and acrylic is the issue. Its just different compositions accomplishing the same thing and both are water based. Do you have any green screen material you can just put up over the wall to try an experiment and see if you have the same issue afterwards? If so, we know its something with your fixtures.
 
By hot spot do you mean a reflection of the fixture, or do you mean that the lighting is uneven?

Sounds like a refection. If you move the camera, does the hot spot "move" on the wall? Then it is a reflection. If it does not move, it is uneven lighting.

If it's a reflection, there is too much sheen in the paint. There is not much standardization in the paint industry as to the meaning of "flat." So it could be calle flat paint but still have too much sheen.

If it's uneven lighting, add diffusion to the fixtures and position them to light the wall as evenly as possible. See Walter Graf's excellent site for more info on lighting greenscreens.
 
It's a reflection for sure. I threw a green screen fabric in front of it and the hot spot is gone. We'll have to buy new paint and repaint the wall.

Thanks for all the advice and suggestions.

Kak Lee
www.myspace.com/kaklee
 
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