Chroma keying

[Mark Suszko]

First bebefit is that the right gree wall color is less likely to come closer to anything worn by people today.

The second point is that green is derived from the luminance channel in many TV sytems so you have a little more picture information from which to generate the key, versus blue. But I think this varies depending on the specific hardware being used.

[Andrew Rendell]

The main reason for going blue or green for the background is that human skin shows a lot of red (even though it doesn’t look red to the eye). Technically the Y signal is more green than blue or red, so in theory green would have a slightly better signal-noise than blue when you derive it from a YUV component video stream, but in my experience it’s not really noticeable (but red would be very poor, and that is noticeable on the occasions I’ve tried it). If you did your chroma key (or colour separation overlay in BBC-speak) in RGB colour space it wouldn’t matter what colour you keyed from, but most of us are dealing with YUV most of the time (e.g., 4:2:2, 4:1:1 or 4:2:0).