Digital Light & Color

The AS Difference View works like a charm, unless a mask is used. With mask, the Difference view, rather than showing neutral gray when the AS didn't affect the input image mask or no mask, shows the original, colour input image where the mask is black (and progressively more watered down to gray when the mask is becoming lighter). Confusing...

I like it that way:) It reminds me that the transformation is being applied to only a portion of the image. For example, the subject but not the background.

OK then :) Let me explain the instance that I found it being confusing: AS with reversed edge masks. In Difference view, the edges show up by virtue of being under the black portion of the mask not because they were sharpened or blurred - which would make them look similar with no mask in the Difference View.