Red Screen Chroma Key (am I nuts?)

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Level 1

5 points

Red Screen Chroma Key (am I nuts?)

Hello:

I have read (don't remember where) that a red background can be used for chroma keying. I have subject matter that is both blue and green (and can't be substituted for other colors) so traditional chroma keying ain't gonna fly. Has anyone had experience shooting and chromakeying red? Is moraying an issue? Is there a particular shade of red that works better?

Also, how do you spell moraying (as in reds turn to mush)?

Many thanks

A

Mac G5

Posted on Dec 29, 2009 11:32 AM

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Answer 1

Dec 29, 2009 2:06 PM in response to Nick Holmes

You can produce a really good matte with the Three Way Color Corrector if you read up on it VERY carefully.

Moiré is a frequency distortion artifact, named for Karl Moiré who held a whalebone hair comb up to his eyes and rotating it while viewing tens of thousands of denuded aspen tree trunks. Or was he looking at tweeds on the mills?

Red turing to mush is a chromatic aberration, the failure of your chosen color space to reproduce on your chosen display system.

bogiesan

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Answer 2

Dec 29, 2009 11:58 AM in response to Verityslice

A Moiré pattern is not caused by an individual colour but by a pattern, the effect seen when a presenter wearing a checked jacket on a tv.

You can 'chroma key' in any primary or secondary colour; red green blue yellow magenta cyan. The problem is whether the background can be successfully cut from the foreground if the foreground contains any colour the background uses, such as a human face which contains red from a red background.

Good results depend on good lighting, good lenses, a good recording system, good keying software and someone who knows what they are doing.

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Answer 3

Nick Holmes

Level 7

30,018 points

Dec 29, 2009 12:06 PM in response to Verityslice

You can chroma key with any color. It just needs to be one that is not in the object that you want to separate from its background. Light it evenly and get the right distance between the object, its background and the camera, you are good to go. Blue is traditionally used because it's the least missed and removing it won't (usually) mess up the coloring of a person's skin tone.

The keyers in Motion are better than those in FCP although you can still do a good job with FCP when the lighting and camera are set up correctly.

Also, how do you spell moraying (as in reds turn to mush)?

Moiré.

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Answer 4

Verityslice Author

Level 1

5 points

Dec 29, 2009 5:31 PM in response to David Bogie Chq-1

Thanks guys. Suspicions confirmed. And thanks for the clarification on "Moiré". I was using the same term for both mushy reds and the pulsing/distortion from tight patterns, etc.

I've run some tests on on a very bright red (scarlet) background (lit beautifully flat) and had the make-up person powder and pamper the skin tones of our model to make sure there was enough color separation. Chroma keyed succesafully in both FCP and Motion. Looks good.

Shooting HD with a Sony PDW-F800 XDCAM. Love this camera.
Just awaiting client approval on the test video then away we'll go.

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