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Green screen light stage

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Zvi Twersky
Green screen light stage
on Jan 13, 2010 at 7:37:42 pm

Ok, we are getting the same light specifications as required but the base of the light we are custom making. Next week we will have a proto type and I'll show it to you.

For now I have a question about the WALL lights positions. From all I read and learned, I had the impression that the wall is lit separately from the subject and that the floor would get lit as a side effect of the key and fill light.

My boss has an impression that the floor needs it's own lights.

I made a 14 second animation showing the setup (for the walls only) that I had in mind and the setup for which my boss had in mind.

Please watch it and tell me witch is correct. (I think his setup has WAY too many lights to the floor.)



p.s. even though I didn't input exact world measurements into 3dsMax, the way you see it in the animation is pretty much the way the spacing would look in real life.


Thank you



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Todd Terry
Re: Green screen light stage
on Jan 13, 2010 at 7:50:27 pm

Ummm...no... your boss's setup is not what you want to do. Unless he has some expertise in lighting design (which, judging from your animation, I'm assuming he doesn't)... then he needs to (as we jokingly say around here) "Stick to his own pay grade."

You want to light your key surfaces completely independently of any talent that is being photographed.

In the setup your boss has concocted, that's impossible. Any talent will be in a downwash of the light that he seems to think is needed on the floor.

Not only does that make lighting the talent independently impossible, but it puts talent in just about the most unflattering light you can imagine. The same reason you don't shoot exterior available-light portraits at high noon on a sunny day.

One question would be... just how often will the floor be needed for keying? If and when it is, light it then. I've not done tons of greenscreen work (mostly because I hate it), but like everyone in our biz I have done my fair share. I don't recall ever specially lighting the floor, even in a full-length shot.


T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com






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Zvi Twersky
Re: Green screen light stage
on Jan 13, 2010 at 8:01:15 pm

Thanks for your reply. It's just what I thought. All that light would end up giving the subject a dull lighting without dimension.

I think most of our shots will be full body shots. My boss is afraid of shadows if there is no light above. I have seen in some places that not only does the key and fill light eliminate some shadows, but many times in full body shots you WANT some natural shadows to be in the shot because it makes a good natural composite opposed to having having to create digital shadows.

I also think that in the worst case, we can always shine 1 extra light from a top side down onto the subject to help eliminate shadows.

Thanks again.



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john sharaf
Re: Green screen light stage
on Jan 13, 2010 at 8:10:50 pm

You are absolutely correct in saying that you want a shadow from the key light. What you want to be careful of is two (or even three shadows) from the fill and/or backlight, this makes the scene look artificially lit, not natural. As always with greenscreen I also advise some consideration as to what you will have in the background. The more you match the direction and quality of the light depicted there on the foreground, the more convincing the effect of the final composite.

When you say however, "I also think that in the worst case, we can always shine 1 extra light from a top side down onto the subject to help eliminate shadows", that is exactly what you don't want to so. If anything, wash out the shadow with a floor light, out of the shot that does not leak onto the foreground subject. Remember most keying deices and programs have "cleanup" which will let you erase the sahhow completely if you wish. This is why sometimes it's best to make a trial composite on set, so you really know what it's going to look like. You can often save a reshoot this way!

JS





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Mark Suszko
Re: Green screen light stage
on Jan 14, 2010 at 3:05:24 pm

You've been given perfect advice. I only add my opinion that, in your setup, make the side lights left and right able to turn off independently of the ones for the back, you want them off when shooting only straight ahead, to reduce chroma spill onto the talent.

If I was doing this, I would take two more instruments like those you've illustrated, position them vertically on stands, just out of shot, washing the wall from the sides. Why?

The way you have it now, you will have a bit of a "ramp" or gradient in light level, higher up top, diminishing at the bottom, and this can complicate the key, which always wants a very even level all the way across the wall. If you later have a shadow problem in full-body shots, one of these vertical lights set off to the side to wash over that spot on the floor will kill it for you, simple.

A simple trick to check for this gradient effect, if you don't have a waveform scope handy, is to rack the camera iris up and down while looking at the zebra bars display in your camera viewfinder. What I am looking for when I do this is for the zebras to kick in, in a uniform way, all across the shot at the same time. If a hot spot emerges much ahead of the rest of the wall, or a dimmer spot lags the rest of the wall, this will point it out quickly.


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Mark D'Agostino
Re: Green screen light stage
on Jan 14, 2010 at 3:17:34 pm

Your boss's plan looks like too many small sources from above that can cause all kinds of shadow issues and make lighting your talent properly just about impossible. I've done a lot of green screen over the past 20 years. We have about a 2,000 sq ft shooting area in our studio with curved and coved hard cyc on two walls. We've often shot wide shots from up high with the talent walking as much as 20 feet across. Our ceiling is only 14' so I cannot place effective top soft light. Because our largest available source is a 4K soft light there are dead areas on the floor so we do hit those with soft lights on stands where we can,(where talent doesn't cross),and let the software help clean the rest. Others with larger softer sources may not have this problem. I'd suggest that you first get your walls lit evenly, then light your talent so that his/her key is 1/2 to 1 stop over what the wall is. If you do see floor and there are dark areas use lights on floor stands, or from a grid to help even those out as along as talent doesn't walk into that space.

I do like the look of a forward thrown shadow and have used a 2k as a 3/4 backlight to throw that shadow. If you are wide enough see the the floor around and in front of the talent's feet avoid any direct back light as this will cause glare on the floor and hurt your composite.

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


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Zvi Twersky
Re: Green screen light stage
on Jan 14, 2010 at 4:02:09 pm

Thanks to you all.

To Mark Suszko:

I did think of your idea but the lights on the top are shaped like half circles and will have panels that can further adjust the light beam (closing them will give a harder hot spot and opening them will widen the beam) so hopefully, this will allow me to make an even spread of light on the wall and not get the gradient pattern.

Of course we will have extra lights on the side so we will play around until we get it right.

I won't forget you guys. Will check in for updates. Thanks again!



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Mark Suszko
Re: Green screen light stage
on Jan 14, 2010 at 7:31:26 pm

Just notice in the vimeo sample video you animated, you can see the gradient falloff problem I mentioned, illustrated by the animated lights in that scene; see how the corners and floor are darker? Barndoors on floods only go so far.


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Zvi Twersky
Re: Green screen light stage
on Jan 14, 2010 at 9:02:17 pm

Yes, you are right about the animation. I just wanted to give a general direction about the tilt of the lights. Of course the lighting in the animation is not even at all. Thanks for the observation.



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