Graphics Programs Reference
In-Depth Information
Keying
Keying, also known as
chroma keying
or
color keying
, is the process of converting
a specific range of colors into the alpha channel, to show the background footage
when layered. The following screenshot shows an example of this concept:
Value and luminance
A clear understanding of the differences between value and luminance is very essen-
tial in compositing since the human eye is more sensitive to luminance than to colors.
It turns out to be even more crucial while keying, since everything in keying is depend-
ent on how you start the process, with respect to a specific channel in a specific color
space. To explain this in detail, the following screenshot will be used, which contains
different tones with at least one of the RGB components having a value of
1
:
The
desaturation
of an image will result in displaying the value of the image. The
value displays the maximum value in between the RGB components. Since the input
