A Photoshop mystery

[Geoff45]

When I use adjustment layers in PS, then sometimes an icon in the third column comes up showing a picture of curves, levels etc, whereas other times there is just a half white/black circle. It seems to depend on the pic in some mysterious way. Can anyone explain this? It's not important, but it just bugs me. Have a look at the two images in the thumbnail to see what I mean:

[sheeny]

Just a wild guess, Geoff, but looking at the sample images you used I'd say the curve adjustment isn't valid for the all black image, so it shows you a "neenish tart".:shrug:

That's my best guess ATM:).

Al.