HMI and Green screen

[Dennis Size]

I also found that adding green gel actually gave us a better key.
I shoot with an HDX900 …. and its shoots beautiful pictures so we make it work for the green screen stuff. I’m be curious if anyone else agrees with that.

Mark D’Agostino
https://www.synergeticproductions.com

I agree with you Mark. The 900 shoots beautifully. Normally I never add green to the light on the greenscreen. When I have, it was only because I had LOTS of distance between it and my subject.. or I had a shoddy greenscreen material.
My preference is always to “warm-up” the subject (with either minus green, straw, bastard amber, whatever works best) to separate him/her from the screen. This helps minimize the green bounce “light source” that trys to “tear” my subject away from the foreground, while changing the quality of the light on the subject — as opposed to the greenscreen.
I always have the greenscreen at least one stop underlit.
Many of my lighting decisions are based on how big the greenscreen actually is, whether or not my subject is also walking around on it, and what type of lighting instrumentation I’m stuck with.
If I’m just doing a simple head & shoulders greenscreen shot I would light it very differently than an entire virtual reality set. Every situation brings with it it’s own set of problems.

DS

[Robin Probyn]

Hi Denis

I thought to cross light the screen with 2 X 1.2 HMI.s through as big as silks the studio has.I,ll have to have the floor lit too,as the hero walks on and then looks to camera(not much moving around)

So not a virtual set,but have to light head to toe..

Any thoughts..?

Thanks

[Dennis Size]

That’s a lot of “firepower”!
How high, and how far offstage are your 1.2’s? A chimera or some sort of softbox to control the spill from your silks will be advantageous.

DS

[Robin Probyn]

Guess I was worried about not having enough firepower… studio is big so can back them off..

Do you think 2 X 575,s would be strong enough through silks.. for the back screen.. 1.2 for the key light on the hero,and floor through silk.. 575 as back/side light..

I will have flags for spill..

Thanks

[Tim Kolb]

As one who both shoots…and then has to pull greenscreen composites, there is a couple things that I’ve concluded.

1. When pulling a screen from a color background, the fact that it’s lit over or under doesn’t seem to be the primary issue…the key factor is that it’s different…over or under. The FX Guide TV guys did a test some time ago with green screens on a Viper camera, lighting at various levels relative to the foreground, and the easiest extraction was pulled from a shot where the green background was lit so brightly that it appeared to be incredibly desaturated. It was simply the shade that was the most distinct from the foreground palette.

2. Daylight lighting seems to help compositing, particularly with skin tones in my experience.

Blue is very nearly across the vectorscope from human skintone and the color of a typical blue screen wall can be moved even more directly opposing if lit with daylight as opposed to tungsten (and this shift becomes even more important with green, as the angle to green is only about 90 degrees) allowing standard spill suppression in most keying applications to work most efficiently.

The other factor to consider is that any video camera is noisier when balanced for tungsten than when balanced for daylight as blue needs far more gain applied to balance with most tungsten sources than red needs with most daylight sources.

TimK,
Director, Consultant
Kolb Productions,

[Michael Palmer]

“the fact that it’s lit over or under doesn’t seem to be the primary issue…the key factor is that it’s different…over or under.”

I couldn’t agree more, if they have the room to separate the green from the subject.

However I believe it is much safer for me when i’m offering advice to the masses to keep the green screen lighting 1.0-1.5 stops lower than the key because I can’t assume their situation or skill level to see light, putting them at risk of creating a moster of green bounce that will contaminate their subject.

I also prefer HMI lights and 5600k white balance for green screen work.

Good Luck
Michael Palmer

[Mark D’agostino]

Hi Dennis,
If you add 1/4 minus green and the cto to the backlight and not the key do you tend to see an odd color rimming the back or do you keep it subtle enough to not notice? I’m guessing if I need my back/rim to be bright and white for effect I wouldn’t need the correction anyhow since it’s already overpowering the potential screen spill.
I mis-typed above and did mean 1-1/2 – 1 stops under key. I always do that because our studio is small and our typical location green screens are in small spaces so I’m trying to lessen green bounce. For simple MS green screens we did indeed get better results when we added the green gel. I obviously can’t do that when we are shoot head to toe stuff with the actors moving across the studio.

Mark D’Agostino
http://www.synergeticproductions.com

[Robin Probyn]

How do you deal with having to light the floor(so to speak) if no grid above.Just flood it with huge soft key?and fill?

[Mark D’agostino]

If it’s a large area with talent moving across a wide shot and you see them head to toe, I start by lighting the walls and floor with large soft sources to get everything as even as possible; keeping in mind that you need room for the talent/prop lights With that done I then concentrate on adding the lighting for the talent and props. If you’re killing all shadows in the final composite then this is relatively easy. If you want shadow,say a single shadow from a back rim, then I light my talent to match the eventual background and tweak that and the studio soft sources to find a good balance of interesting talent light and even studio light. I avoid a direct back light because of the glare, (There is a gel I found years ago that can be put on your key light that acts as a polarizer. When you rotate the barn doors it kills the glare. This is only useful on a fresnel and I never could use it because it took about 1-1/2 stops from my key and all my sources are relatively small).

Mark D’Agostino
http://www.synergeticproductions.com

[Robin Probyn]

checked out studio at last.will go tungsten as their over head soft lights are tungsten. couple of 2 ks for the back wall though silks.5k key.. 2k back/side light..

Kino,s for close ups..

Thanks