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
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.
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