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Green screen lighting set up


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#1 Eugene Lehnert

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Posted 12 May 2006 - 11:27 AM

I have 3 650 watt Arri lights. I want to purchase a green screen to start doing some lighting tests with. Any advice on the set up? Basically I just need to get the green screen as even as possible without getting any spill on the actor? Maybe I should pick up some more lights?
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#2 Matt Irwin

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Posted 12 May 2006 - 11:41 AM

I'm assuming you're on a budget, so I would recommend buying some fluorescent shop lights. They suck in the field but for green screen, they work well. You'll probably find 2 bank or 4 bank T12 fixtures with integrated ballasts and a shaped aluminum frame.

You can lay some on the floor angled back toward the green screen, mount some to stands at the sides, maybe hang some above the screen if you want. (Usually 2 fixtures on either side does the job for a small screen). No real need for special color correct tubes. Just use cool whites, but make sure your talent isn't hit with any spill.

Of course you could try to diffuse your tungsten lights, but flos are already fairly soft and have a wide spread in those shop lights.
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#3 Chris Cooke

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Posted 12 May 2006 - 01:22 PM

I would suggest lighting your screen one stop under key to reduce green bounce from the screen onto the talent. It can also be a good idea to put some 1/4 minus green (a majenta gel) on your backlight to help with the composite. Don't use anything heavier than 1/4 unless you want your talent to have an obviously majenta backlight. Have pictures or video on set of what you will be compositing behind your talent. This gives you a chance to visualize what you are lighting and where the motivation is coming from.
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#4 Laurent Andrieux

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Posted 12 May 2006 - 04:51 PM

This subject has been discussed many times here around, make a research.

For sure the former advices are good, I would say that as far from the BG as possible you can have the talent the better it will be. No green reflections on him/her/them, no spill of light on the green screen...
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#5 Michael Nash

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Posted 12 May 2006 - 04:53 PM

Has anyone tried compositing with HDV's long-GOP compression? Yikes...
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#6 Matt Irwin

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Posted 12 May 2006 - 05:56 PM

Has anyone tried compositing with HDV's long-GOP compression? Yikes...


I shot some green screen a while ago with a Z1U. End result wasn't horrible, but the talent was barely moving at all. I had nothing to do with the post, but I think it was carried all they way through in HDV-- no cross/upconvert.
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#7 Eugene Lehnert

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Posted 15 May 2006 - 10:01 AM

Is there any benefit to create a narrow depth of field when shooting on a green screen? Setting the camera at a distance that would throw the green screen out of focus and the subject in focus? Would this be beneficial?
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#8 David Mullen ASC

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Posted 15 May 2006 - 10:58 AM

Is there any benefit to create a narrow depth of field when shooting on a green screen? Setting the camera at a distance that would throw the green screen out of focus and the subject in focus? Would this be beneficial?


You want the subject to be in focus in front of the screen, so too shallow a focus is not a good idea. It doesn't help one way or the other for the screen to be out of focus. What helps to to have an evenly-lit screen that is large enough and far enough away and flagged to reduce spill on the subject. The big mistake people make is using a screen too small and too close to the subject, causing it to bounce the chroma-key color onto the subject, and not light the screen evenly.
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#9 Chad Stockfleth

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Posted 15 May 2006 - 12:33 PM

You want the subject to be in focus in front of the screen, so too shallow a focus is not a good idea. It doesn't help one way or the other for the screen to be out of focus. What helps to to have an evenly-lit screen that is large enough and far enough away and flagged to reduce spill on the subject. The big mistake people make is using a screen too small and too close to the subject, causing it to bounce the chroma-key color onto the subject, and not light the screen evenly.


What if you need to shoot someone head to toe on a green cyc? I've done this a few times for spots with mixed results. Tough to keep bounce off of shoes, etc.
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#10 David Mullen ASC

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Posted 15 May 2006 - 12:49 PM

What if you need to shoot someone head to toe on a green cyc? I've done this a few times for spots with mixed results. Tough to keep bounce off of shoes, etc.


It's a nightmare. You do what you can. I've had to add some extra lighting to the feet to wash out the green spill better, but that makes me nervous -- I'd hate to see someone pasted over a new background and have their feet look oddly overlit, but if the lighting gets too murky down there, you can get too much green spill.

Haven't tried the mylar floor trick.
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#11 Chad Stockfleth

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Posted 15 May 2006 - 01:15 PM

It's a nightmare. You do what you can. I've had to add some extra lighting to the feet to wash out the green spill better, but that makes me nervous -- I'd hate to see someone pasted over a new background and have their feet look oddly overlit, but if the lighting gets too murky down there, you can get too much green spill.

Haven't tried the mylar floor trick.


On one job we had to shoot a girl walking in and sitting in a plush chair on the green cyc. Everything looked good except for the shadow underneath the chair, it wouldn't key. We tried putting a small light aimed under there, but it caused too much spill on the legs. The answer? Taping a white card to the bottom. Brought the shadow into a reasonable lum and keyed like a dream!
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#12 Phil Rhodes

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Posted 15 May 2006 - 03:31 PM

Hi,

That retro-reflective system seems decent, but it's quite expensive.

Phil
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#13 Eugene Lehnert

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Posted 17 May 2006 - 04:31 PM

The room we are going to be shooting in is going to be fairly small. Not tiny but not gigantic. About 15 feet by 20 feet. The green screens shots are merely going to be interviews. So I got the ok to rent some better lights. I was thinking some decent flourescents because they would be cooler and less power. I was going to go to www.hotlights.com to rent them. My green screen is 9 feet wide and 10 feet high or more. We only have one car to transport this material. I was testing everything out with two 650k fresnels with diffusion on the front and I was getting a fairly good key. The lights definately needed to be farther back to diffuse the light to get a more even spread on the green screen though. I was also getting a lot of spill from the white walls in the room we were shooting in. I am bringing some black muslin to hang off of grip stands to cut down on that.

Are flourescents practical and portable? Two on either side? How much wattage can I expect to see from a 4ft 2 bank system?

Your advice and experience is appreciated.
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#14 David Mullen ASC

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Posted 17 May 2006 - 05:17 PM

You could easily light a 9x10 greenscreen with a 4' 2-banker on each side, maybe a third one on the floor shining up at the middle, with Kino greenscreen tubes.
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#15 Michael Nash

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Posted 17 May 2006 - 05:26 PM

For interviews framed MCU in a room that size, I think a 4' 4-bank on either side should be more than adequate. Get the 4-bank rather than the two just in case, since you can switch off bulbs you don't need or use all four with diffusion if you like. Kino-flo's are very portable and lightweight, but you'll need C-stands (and sandbags) to mount them. If you're new to Kinos have your rental house give you a quick demonstration on how to set them up (it's easy).

You could position one on each side mounted vertically, or for a more even spread try turning them horizontal and just above frame line, with the stands just outside frame edge (not too close to the green screen, though.

I would use the longest axis of the room with the screen against one wall and the camera backed all the way up to the other. That will allow you a slightly longer focal length and some "room" to position your light stands. Put the subject about 2/3 of the way across the room from camera. And it probably goes without saying you need to make sure you green screen is stretched tight with no shadows from ripples. Sometimes that's a challenge when the screen isn't strung up on a frame.

Regarding head-to-toe green screen, soft lighting is your friend (at least at the feet). Sometimes it takes some strategic flagging to get a soft quality of light (no shadows) while still having the desired modeling on the rest of the subject.

But the "key-ability" of shadows really depends upon the compositing system. I've seen some systems effortlessly pull beautiful keys from contact shadows, while other (supposedly higher-end) systems completely freak out and fail at the slightest blemish (from the same source material). Of course the best thing is to make the screen as "perfect" as possible, but sometimes difficult situations simply require more post work.
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#16 Eugene Lehnert

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Posted 18 May 2006 - 12:35 PM

Excellent. Thanks for the advice.

What are Kino green tubes? Are these made specifically for green screen work? How are these different from tungsten balanced tubes?
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#17 David Mullen ASC

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Posted 18 May 2006 - 01:16 PM

Kino green and bluescreen tubes (and their Super-Blue tubes) put out a very narrow bandwidth in one color, so the green or blue is very pure. In fact, you could use a white sheet practically and turn it into a greenscreen with a Kino green tube, as long as there was no other stray light hitting the screen. And it doesn't make as much difference whether you use a ChromaKey Green or Digital Green material, other than reflectivity, because the color you get is basically what the tube puts out.

I once used some Kino blue tubes in a nightclub location for a blue neon effect (super deep blue color) and noticed when I pointed the blue tubes at a red wall, they registered as gray walls since there was no other colors mixed into the output of the tube.

Normal lights like from tungstens or HMI's are full-spectrum sources, so they have all colors mixed in there, just that they are biased towards one end of the color temp range.
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#18 Eugene Lehnert

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Posted 18 May 2006 - 03:46 PM

That's really interesting. I'll see if I can give that a try.

Thanks!
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#19 Eugene Lehnert

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Posted 20 May 2006 - 10:03 AM

Wow! Thanks David. That advice for using the Kino Green bulbs was truly awesome. They worked out like a charm. I've never been able to pull a better key before. The light was so perfect and even. I shot with the HVX doing interviews with P2 cards and we had Shake on site to check the keys and with little to no effort we could pull a near perfect key. And the room was smaller then they said! With a few mirrors all over the room. But with the room covered in black muslin it worked out. Thanks again. That rocked.
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#20 Michael Nash

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Posted 22 May 2006 - 07:29 PM

Has anyone tried compositing with HDV's long-GOP compression? Yikes...


Sorry, I just realized he was talking about the HVX, which isn't HDV. HDV is long-GOP; HVX records HD as DVCPRO HD (intraframe).

Oops.
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