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Formats for chroma keying

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Johannes Nyholm
Formats for chroma keying
on Jan 5, 2011 at 2:18:55 pm

I wonder what would be the best and worst formats for green screen chroma keying of these:

1. ProRes 1920i 422
2. ProRes 1920i 444
3. Uncompressed 1920 8-bits


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Richard van den Boogaard
Re: Formats for chroma keying
on Jan 5, 2011 at 3:43:10 pm

Hi Johannes,

The more detail is recorded in the image, the better your key will perform when doing green screen work.

Therefore, if you record in ProRes 4:2:2 or better yet 4:4:4, it will work better than a 4:2:0 encoded file. What will not help you much is transcoding of compressed 4:2:0 footage to 4:2:2 or 4:4:4 ProRes. As far as I know, there are not a lot of cameras that allow for native ProRes recording (ARRI Alexa does), although some cameras offer a 4:2:2 SDI output signal which can be recorded on a separate recorder.

I don't have experience yet how DSLRs perform with green screen work. Maybe someone here on the forum does...

Richard van den Boogaard
Freelance cameraman • Glidecam Operator • Editor • YouTube expert

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Dave LaRonde
Re: Formats for chroma keying
on Jan 5, 2011 at 4:34:23 pm

As Richard says, the color resolution (4-2-2, 4-2-0, etc.) is crucial. Since cameras record their video in different color resolutions, a better and more expensive camera will record using better color resolution than an inexpensive one.

However, you can sidestep the issue.

If you have the proper equipment -- an AJA I/O box, for example -- you can hook a camera's HDMI output to it, and capture full 1920x1080, 4-4-4 video in a lossless codec, if you wish. Such gear isn't cheap, and if you're on a budget, you hay have to simply live with what you've got.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA

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