I have discovered that setting Calccapture to Greyscale (256 Colors) dramatically increases the file size and also slows down frame rate. In some games this may be ok, but for others, the fps stuttering will be unbearable. Eg: on Cubefield it was bearable, on Gravity Guy it just didn't work.
However sometimes color produces a faster fps rate than it should.
BIGEDIT!!!:
Just added stuff and detail to my moving screenshot I created over a year ago. See first post. Should put this up in the tutorials section.