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Tips for using green screen paint to create a small prop

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Miki Trimbe
Tips for using green screen paint to create a small prop
on Mar 26, 2016 at 11:30:33 pm

Hi,

This is my first post, so I hope it's in this is an appropriate section for it! I'm directing a sci-fi short film, and in it, one of the characters is going to be holding an a4 size piece of glass. We're planning to use green screen paint to paint in a 5 x 7 inch rectangle inside of it, and use fx to make it look like a futuristic sort of glass ipad, with text appearing on the 'screen'. I'm not super knowledgeable about sfx since my friend is the person doing the post production. I'm just looking for tips on what I can do to set up the set design to make the color keying process successful for this. Any help would be deeply appreciated!

Some details to note:
- the glass tablet will be sitting on an ipad stand, on top of a glass table. I've read that there are some concerns regarding the green screen colour reflecting off glass...
- the lighting is going to be very bright and flat, and cold white
- the object is going to be moved around: first the character picks it up, then there is an over the shoulder shot of the tablet, then they put it down on the floor and meditate in front of it, before picking it up again


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Todd Terry
Re: Tips for using green screen paint to create a small prop
on Mar 27, 2016 at 12:17:25 am

Well, a few thoughts...

Firstly, ask your friend who is doing the post for input. That should be step number one.

After that, a few things to think about...

If you want to paint a rectangle on the glass, but are worrying about reflections from the glass desk below it, you can do a couple of things. Firstly, mask off the rectangle you want to paint, and then paint it black, not green. Then paint it green. That would leave you with greenscreen on top, but no green visible from the underside to cause worrisome green reflections. Personally, I wouldn't paint it at all... I'd cut a piece of green paper (readily available in a zillion colors from craft stores) and spray mount it onto the glass (again, you could use paper that is green on one side, not green on the other). That's a lot easier and faster than painting.

Secondly, think about your shots very carefully. Unless you are blocking your shots in such a way that something (a person's hands, etc.) violate the "screen" area, you don't even need the green at all... you'd just composite and motion-track the inserted video onto the appropriate area of the glass.

If the case is that you might have some shots where the screen is violated and some that they are not, you might make two props...one with the green on it and one blank. You can use the blank one for all the shots where it is shown clean (with no fear of any reflections), and use the green one only for ones where it is violated by hands or whatever.

A lot of times when you see this effect done, whether it be in Minority Report or about a zillion other movies, the images on the glass are a bit transparent. If that is your goal, obviously you don't want to use greenscreen at all, just the clear glass and composite it on later. A couple of tiny spike marks on the glass might help compositing and tracking, but might not be necessary all. If hands or anything else violates the field of view, they would have to be rotoscoped for the offending frames.

There are lots of ways to do this, but those are my first thoughts. Hope it helps.

T2

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



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Miki Trimbe
Re: Tips for using green screen paint to create a small prop
on Mar 27, 2016 at 12:55:15 am

Thanks for the tips, these will definitely come in handy. About the green paper technique--do you think that would work? Do you think it might be risky in terms of getting the correct shade of green? I heard that the green screen paint is made without any other pigments which is what enables the process to work without any hitches.


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Rick Wise
Re: Tips for using green screen paint to create a small prop
on Mar 27, 2016 at 12:19:35 am

Shadows and reflections can cause problems. If the object is sitting on a glass table, then you may have green reflection problems. Perhaps the object can be on some sort of stand that lifts it off the table, and possibly there's some kind of cloth under the stand as well. After that, make sure that hands/arms don't cast shadows on the "tablet." It will help a lot if the green object is the same size as the keyed object and of similar weight.

Your success will depend a lot on the software used to create a key. You might post to one of the forums addressing whatever software your client is using. I see you have posted also on DigiEffects, which is a good idea.

Rick Wise
Cinematographer
MFA/BFA Lighting and Camera Instructor Academy of Art University
San Francisco Bay Area
http://www.RickWiseDP.com


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Miki Trimbe
Re: Tips for using green screen paint to create a small prop
on Mar 27, 2016 at 12:56:51 am

Thank you for the help! Will definitely be asking my friend about the software to finish planning everything out as smoothly as possible


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Mark Suszko
Re: Tips for using green screen paint to create a small prop
on Mar 28, 2016 at 5:10:12 pm

Late to the party with my two cents.

Greenscreen seems easy at first for this, but green alone doesn't give you the constant perspective changes that you get by motion-tracking the blank piece of glass. It will look like a shaky telescopic close-up of the target image, instead of an image actually emitting off the screen.

So, since you're gonna wind up having to motion-track it ANYWAY - don't bother adding any green at all, except for perhaps the "spike marks" Todd suggests.

I'll go further to suggest you make 4 little L-shaped marks on the corners of the glass, semi-translucent ones, could be done just with frosted cellophane tape - and that's your complete prop, ready to use. This gives you the semi-transparent base you need anyway, and the frame L-corners give you the needed tracking markers.

Or, you could adhere a translucent piece of colored gel to the glass - either a little piece of ND, or maybe light blue, indicating a "standby condition" on the display.


you'll get something like this:







or this:









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