"Mark Carver" wrote in message
...
On 13/06/2019 16:31, NY wrote:

As a matter of interest, why is it that they used to use blue backgrounds
and keying for Chromakey but nowadays almost always use green? I thought
that blue was chosen because it was the least likely primary to be
contained in the foreground subject, and the most diammetrically opposite
to flesh tones which are the absolute worst thing that they want to cause
false triggering.

The use of blue was a throw back to 'film chromakey', which I think was
the easiest colour to separate out in that process.

Green is chosen for contemporary video chromakey, because it constitutes a
higher proportion of the signal, requires less illumination, and therefore
generates a better 'mask'.

I thought the film had used green (or in some cases, sodium yellow) for
along time as the matte-out colour, and that TV had gradually changed from
blue to green as so to fall into line with film practice.