Want to create a mask based on saturation

[kkamin]

Is there a way to make a mask based on an image's saturation? I'm trying to pull a mask from an image of a color subject on a black and white background.It is a composited shot and the background is completely gray scale--while the subject has some color variance, even in the seemingly neutral areas.



Any help is much appreciated.

[Der_W]

Of course there is :-).

Assuming you're in RGB mode: https://www.youtube.com/watch?v=9xCo-nKpMSU