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Tricky Green Screen Shoot Requires Your Brain Power

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Timothy Ford
Tricky Green Screen Shoot Requires Your Brain Power
on May 30, 2009 at 8:13:41 pm

We want to shoot a spot that involves an person with a glowing aura watching a virtual video wall. I can handle the the visual effects portion of this, but I'm a little puzzled as to how we can pull this off in the field. You see what makes it tricky is that there will be camera movement, and we need to composite the actor in a real environment. The best approach I can think of is:

1. Shoot the actor against the green screen with the camera move (we start on his face and rotate to an OS position, then part of the way back)
2. Then we shoot the plate without the actor in the scene and try to match the camera move as closely as possible.

I have no illusions about how difficult this could be. Just to get the green screen shot will require a chroma field that covers about 270 degrees.

How are these types of things done? A motorized dolly? What about controlling the pan and tilt?

Any information you can provide or direct me to regarding advanced green screen production technique will be helpful.

Thanks.


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Mark Suszko
Re: Tricky Green Screen Shoot Requires Your Brain Power
on May 30, 2009 at 10:43:30 pm

Motion-controlled camera makes the moves all repeatable, this is the most efficient but expensive and complex way.

If you don't mind shifting costs to the post production side, I would suggest conventional green screen plus adding some small markers to that screen. Then motion-track the screen in AfterEffects or a similar compositor. Once you have the motion tracked, you can apply the data to all elements in the composition and they will all stay locked together no matter how the camera moves.

(Added edit) Remember too, that in an all-green environment, you can get the same effect as a curved-track camera dolly, cheaper, by just putting the actor/chair on a green turntable and rotating THAT. Though to make that really convincing, you'd probably want to also adjust the lighting as you go, just a little bit.


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Timothy Ford
Re: Tricky Green Screen Shoot Requires Your Brain Power
on May 31, 2009 at 4:21:50 pm

Thanks so much for weighing in Mark. Motion Control is what I was looking for. I'm most concerned with getting a realistic composite between the staged actor and the real environment so I'll most likely propose this solution. If we were using artificial backgrounds then I'd just track it in post and save us a bundle, but there is just too much to consider regarding perspective.

I had thought of the Lazy Susan idea myself, but was concerned about the lighting. This will be the contingency plan. We'll just make the camera move less complex and rotate the actor.

Thanks again. Your post was very helpful.


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Adrian Sancho
Re: Tricky Green Screen Shoot Requires Your Brain Power
on Jun 1, 2009 at 7:47:08 am

>>I'm most concerned with getting a realistic composite between the staged actor and the real environment...<<

Isn't it easier to synthesize the "real environment"? Then you can matchmove the keyed actor (which essentially becomes the "real environment") to make a perfect sync, no?


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Timothy Ford
Re: Tricky Green Screen Shoot Requires Your Brain Power
on Jun 1, 2009 at 10:26:29 pm

Yeah this would be the ideal method, but it's supposed to be in a laboratory or classroom of sorts, and I'm not sure my matte painting skills are quite there yet.

Do you know of any resources/tutorials regarding this subject. Matte painting that is?


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Adrian Sancho
Re: Tricky Green Screen Shoot Requires Your Brain Power
on Jun 3, 2009 at 5:55:01 am

Why not just put your room environments on planes in a modeler? Matchmove to your live action.


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Jack Sammanson
Re: Tricky Green Screen Shoot Requires Your Brain Power
on Jun 9, 2009 at 8:48:58 pm

For a 360 view, you could use a trick that Robert Rodriguez has used in his films.

Set up your green screen so it completely covers the frame, and have your actor in front of it, standing on a rotating stool (piano stool, or office chair with no backing or arms, etc.). Now simply have the stool rotate while he/she is on it, and move the camera however you like, making sure you do not film the stool.

Now in post, simple animate the environment so it matches his movement, and there you go! Simulated camera movement!


-Jack


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Curt Pair
Re: Tricky Green Screen Shoot Requires Your Brain Power
on Jun 17, 2009 at 2:13:37 am

We've used Jack's method too, and it works! If you are TRULY worried about the rotation apparatus, paint it green, cover it, what have you!

You'll more than likely surprise yourself! Don't over think it, try to simplify it!

Do you have time/budget for a test shot? That will help too! The second time around will be easier! If you CAN... try taking a laptop... bring in a clip or two, if possible, and try the key right there! You'll learn what's working and what's not! If you try that... shoot the plate FIRST, then match the motion when the actor is in front of the chorma wall.

Curt Pair
Picture This Productions
Sony ICE Team
F900/F800/F350/PDW700/EX1/EX3/D790/D600
Adobe Premiere Pro CS3 HD/Matrox
Phoenix, AZ


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Timothy Ford
Re: Tricky Green Screen Shoot Requires Your Brain Power
on Jun 17, 2009 at 11:30:07 pm

Indeed. I've been doing my homework and studying up on some VFX breakdowns recently. I saw the SIN CITY OPENING - GREEN SCREEN BEFORE AND AFTER video which illustrates this principle clearly. I'm surprised at how much you latitude you can have with a key.

We will not have time/money for another practice run with this one, but I'm confident enough with the mechanics of the shot that I've decided to recommend this route. We may need only to simplify the move.

Thanks so much for your input on this everyone. The comments have been very helpful.


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