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Lighting for Blue Screen/chroma keying

Hi guys,

I don't have much experience in blue/green screen so sorry for the dumb question. So I've watched tutorials on Youtube and I have a set up in mind.

I will light the blue screen with two Kino Flo's(daylight balanced).

In front of the blue screen will will be two presenters, the director wants this to be lit in tungsten light. This will be mixing colour temperatures in the shot.

Obviously I will white balance for the the presenters. However, my concern is, will the light coming from the Kino's become really blue and spill onto the presenters? The space is a bit tight so the presenters can't be too far away from the blue screen.

Thanks
 
If this is paid work, I urge you hire VFX Supervisor who has done this before.

You don't have much experience? How much experience do you have (number of setups, conditions etc). Who is pulling the key in post? What is their experience level?

What is the specific reason you selected blue as your color? There's nothing "wrong" with this selection, but there should be a reason for every technical decision you make.

The following are a few notes to consider, but is BY NO MEANS a how-to lesson. If any of this seems foreign to you, there's a chance you're going to get yourself into trouble:

** MOST IMPORTANT: Shoot some tests, take detailed notes, and run a composite. Many productions ignore this and simply assume that everything can be fixed in post. If you shoot junk, you will need an talented/experienced/expensive person to pull the key.

- The distance from the screen is very important. Anything closer than 10-12 feet will introduce spill.

- Foreground vs Background exposure is critical.

- Back lighting your subjects with an appropriately gel-ed light can go a long way in canceling some spill, and give you a cleaner edge to pull (hair particularly).

- Even lighting is important. Modern compositing tools are able to apply multiple keys for poorly lit screens, but again, this makes shot completion very difficult to the inexperienced Compositor. Check your screen with a spot meter. Failing this, hire a VFX Supervisor to check the lighting. Failing this, try this iPhone app: Green Screener . Although I've never used it, I know a guy who tried it out and said it wasn't bad.

- In order to reduce spill, keep the screen as small as absolutely possible. Mask any part the screen that's not needed with black duv. Hang the duv as far from the screen as possible.

- What codec are you capturing? It makes no sense to shoot a perfectly prepared screen, if your camera doesn't maximize color information (H.264 does NOT give professional results).

Cheers,

Thomas
 
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Hi guys,

I don't have much experience in blue/green screen so sorry for the dumb question. So I've watched tutorials on Youtube and I have a set up in mind.

I will light the blue screen with two Kino Flo's(daylight balanced).

In front of the blue screen will will be two presenters, the director wants this to be lit in tungsten light. This will be mixing colour temperatures in the shot.

Obviously I will white balance for the the presenters. However, my concern is, will the light coming from the Kino's become really blue and spill onto the presenters? The space is a bit tight so the presenters can't be too far away from the blue screen.

Thanks

I don't understand the reasoning for the two different color-temps. They're going to bleed into each other. You said that space is tight, so that means that there will be lots of bounce off of walls and stuff. I highly recommend keeping all lights on the same color-temp. How do you white-balance for the presenters, when you're using two different colors of lighting? Are your presenters literally the color white? Cuz that's the only way you could truly color-balance to them. I think it's going to look weird.

To answer your question, yes you need space between your subjects and the bluescreen. How much space you need depends on how much wattage you're sending it's way, vs how much wattage is on the subjects. So get specific. What is the size of the room? What is the wattage of the lights you plan to use?
 
It's just a project with some friends, so not super important, but obviously I wanna learn how to do it well.

When I say white balance for the presenters I mean white balance for the lighting used on them.

Basically they want the presenters to be lit in tungsten light to give it a cozy feel. So the white balance for them would be 3200k.

Now to light the blue screen I have two Kino Flo's(day light balanced bulbs), so now we have two conflicting colour temperatures. If that is going to cause issues, then could I just stick some CTO gels in front of the Kino Flo's so now all the lights have the same colour temp? I was just worried the orange tungsten light may cause issues for the blue screen to be keyed out, but if it's not then I will do that?

Here is the room http://i.imgur.com/VTlevLw.jpg?1

The blue screen will be placed where the window is.

So the lights I have are:
x2 800w red heads, dimmable
x2 300w fresnels
x1 150w fresnel
x2 Kino Flos(I don't know the wattage, but theres 3 bulbs in each)
x2 LED light panels(probably 300)

Thanks for the suggestion on the Green Screener App, Ill give it a go.

I'll be filming on a Blackmagic URSA Mini 4K, filming in Pro Res 422. I will be filming in REC709 as they don't plan on doing much grading. Will Pro Res 422 be sufficient for chroma keying, or willl doing it in HQ make a big difference? Would definitely prefer to shoot in 422 for hard drive space.

Thanks for the replies
 
"It's just a project with some friends, so not super important"
This lowers the stakes. Good place to learn. Take notes and have fun.

"could I just stick some CTO gels in front of the Kino Flo's so now all the lights have the same colour temp?"
Yes.

"I was just worried the orange tungsten light may cause issues for the blue screen to be keyed out, but if it's not then I will do that?"
If you are balanced for tungsten, then lighting the screen with tungsten is normal. What's your reasoning behind using blue?

Will Pro Res 422 be sufficient for chroma keying, or willl doing it in HQ make a big difference? Would definitely prefer to shoot in 422 for hard drive space.
I've done this. It's fine for what you are doing.
 
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