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Lighting Actor Greenscreen Simulating Sunlight Shadows

lighting green screen

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#1 Johnny Harris

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Posted 14 July 2015 - 02:45 PM

I'm new at this and have a quick question that maybe someone with more experience could give me a heads up on:

 

I need to shoot an actor (full body + shadow) against a green screen INSIDE. That part is okay.

 

Problem is I need to make it look like it was shot in sunlight from a shadows point of view.

 

When composited, the studio light gives distorted shadows because of the close proximity of the light to the subject (a few feet) as opposed to the backplate (the sun, a couple of million miles).

 

In CG (my previous gig) this light would be called 'infinite light'.

 

How do I get parallel light (infinite light) crisp looking shadows inside my space which is 14' high.

 

Can it be done & how?

 

I've tried researching the net but maybe I'm not using the right keywords.

 


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#2 Albion Hockney

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Posted 14 July 2015 - 03:04 PM

what does "from a shows point of view" mean exactly.

 

generally to simulate sunlight you just use larger lights farther away. if all you are doing is lighting on person, if you can shoot at a reasonable F stop 2.8/4 and have a modern camera shooting 800ISO you could probably get away with something between 2000 and 5000w or something like a 1.2K HMI Par would work.

 

you also need to factor in the fact that there is natural fill light from the blue sky and the sun bouncing off other objects like white/grey cement on the ground. generally the way people do this in studios is with a grid of overhead space lights that give a general ambiance and then use one big strong light for the Sun


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#3 Johnny Harris

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Posted 14 July 2015 - 03:44 PM

what does "from a shows point of view" mean exactly.

 

generally to simulate sunlight you just use larger lights farther away. if all you are doing is lighting on person, if you can shoot at a reasonable F stop 2.8/4 and have a modern camera shooting 800ISO you could probably get away with something between 2000 and 5000w or something like a 1.2K HMI Par would work.

 

you also need to factor in the fact that there is natural fill light from the blue sky and the sun bouncing off other objects like white/grey cement on the ground. generally the way people do this in studios is with a grid of overhead space lights that give a general ambiance and then use one big strong light for the Sun

 

Thanks for the reply and the help. Sorry for not being more explicit.

 

From the shadows point of view meant that I wasn't talking about color temperature etc (althought you brought up some REALLY GOOD POINTS in your second paragraph). As I'm sure you know shadows get distorted pending on how close the light is to the subject.

 

Perhaps I can illustrate this point better with this reconstruction in cg. One is a spotlight, the other is a distant light that would be the equivalent of the sun. Note the shadow difference although both lights are from the same angle.

 

https://flic.kr/p/vJ5XTm

https://flic.kr/p/vYo8Jm


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#4 David Mullen ASC

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Posted 14 July 2015 - 04:32 PM

Can't really be done but perhaps you can get close enough -- you could perhaps increase the apparent distance of the source by bouncing it into a large mirror but it would have to be pretty large, not sure a 4'x4' mirror on top of a 14' ceiling would create a large enough pool of light from a reflection to cover someone head to toe.  But if it did, you could effectively double the distance of the source from the subject and get less of a spread from the shadow.

 

The best thing would be to drag your green screen set-up outside into the sun...

 

Or find a bigger stage with a higher ceiling.

 

Perhaps the black shadow itself (I assume it's on the ground but it could be a wall) could be isolated in post from the body and distorted to correct the amount of spread.


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#5 Johnny Harris

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Posted 14 July 2015 - 05:44 PM

Can't really be done but perhaps you can get close enough -- you could perhaps increase the apparent distance of the source by bouncing it into a large mirror but it would have to be pretty large, not sure a 4'x4' mirror on top of a 14' ceiling would create a large enough pool of light from a reflection to cover someone head to toe.  But if it did, you could effectively double the distance of the source from the subject and get less of a spread from the shadow.

 

The best thing would be to drag your green screen set-up outside into the sun...

 

Or find a bigger stage with a higher ceiling.

 

Perhaps the black shadow itself (I assume it's on the ground but it could be a wall) could be isolated in post from the body and distorted to correct the amount of spread.

 

 

Great tips. Thank you.

 

Just so I know for future reference, what distance would normally be required for something the size of a person (standing up) to achieve such a look?

 

What ceilings would one be looking at to acomplish that in a controlled environment such as a studio?

 

Thanks again.


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#6 David Mullen ASC

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Posted 14 July 2015 - 06:12 PM

There is no formula, it's just the farther the light, the less spread of the shadow but also the less intensity of the light, so there are practical limitations usually.  You'd probably want to look at stages with well over 20' tall ceilings, the higher the better, but then you have to figure out how to mount the lamp and operate it.  


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