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Blue screen for ice sculpture

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john younger
Blue screen for ice sculpture
on Aug 24, 2011 at 6:22:59 am

Hey all will be shooting an ice sculpture on a blue screen. Will the opaque ice create any problems when trying to key? Any tips would be greatly appreciated.
Thanks in advance.
John Younger


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Tudor "Ted" Jelescu
Re: Blue screen for ice sculpture
on Aug 24, 2011 at 8:10:50 am

Make sure that you can set the ice sculpture as far away from the chroma screen as possible. This way you will eliminate any color spill. If it's opaque ice then you should be fine, unless there are some really thin parts where the color can be seen through. If so, you'll need to roto.

Tudor "Ted" Jelescu
Senior VFX Artist


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Joseph W. Bourke
Re: Blue screen for ice sculpture
on Aug 24, 2011 at 12:59:56 pm

If you have the time (yeah...right...ice melts doesn't it?) you might want to check out where you're seeing blue spill, if any. The most likely culprits will be on the edges of the sculpture where the ice is more transparent or translucent. This could create a nightmare with pulling a good key. As Ted said, distance is your friend, but look for rogue blue spots in the ice - ice has pretty random reflectance where it's transparent, because, unless it was frozen with no bubbles, and is perfectly clear, it will have some funky internal reflecting planes.

If you do have the time, besides following Ted's good advice, see if you can put any bounce cards or reflectors around the sides of the sculpture to blow out any blue leakage, or to create reflections which are stronger than the blue spill. It's going to be tricky, but it can be done. To control the front reflections, short of blue spillage, you might also want to place some small black reflectors and white reflectors to control the overall sheen of the surface. This works best on totally shiny metallic items such as trophies and jewelry, but it could also come into play for the shinier parts of the ice, which has almost the same index of refraction as glass.

Joe Bourke
Owner/Creative Director
Bourke Media
http://www.bourkemedia.com


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Steve Brame
Re: Blue screen for ice sculpture
on Aug 24, 2011 at 1:07:48 pm

Back before Serious Magic was acquired by Adobe, we used their Ultra product very successfully to key a glass of water. Neither Keylight nor Primatte were able to do it successfully.

Now that Ultra is a part of the CS5+ suite, you might want to give it a try before any roto in AE. Certainly worth a shot.

Steve Brame
creative illusions Productions


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john younger
Re: Blue screen for ice sculpture
on Aug 24, 2011 at 7:03:39 pm

Thanks guys will experiment with these techniques and let you know. You guys rock as always.
Thanks
John Younger



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Darby Edelen
Re: Blue screen for ice sculpture
on Aug 25, 2011 at 5:19:10 pm

I would definitely recommend shooting a test on a black background and using Unmult to generate a matte (http://www.redgiantsoftware.com/blog/2010/08/17/knoll-unmult-free/).

This has a ton of advantages over trying to chroma key mostly transparent objects (no color cast, fast to generate a matte). It doesn't work in every case, but I'd still recommend shooting a test.

Don't get too focused on green/blue screens without considering other options.

Darby Edelen


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Walter Soyka
Re: Blue screen for ice sculpture
on Aug 25, 2011 at 5:26:28 pm

[Darby Edelen] "I would definitely recommend shooting a test on a black background and using Unmult to generate a matte "

This is a great suggestion!

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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