Quote Originally Posted by Roger Clark View Post
The way to find clipped areas is to use the levels tool. Hold down the alt key (on windows) and move either the right or left sliders. The image will go black but as you move the slider away from the limit, if any data are clipped it will show as a color. The color and intensity depends on how many channels and how much it is clipped.
Curves also works this way with the right and left sliders.

(Just to be clear) Leaving the slider at 0 or 255 shows you what you have, moving them shows you what you will have if you make that adjustment. The color is which channels are at 255 or 0 for each pixel (for the right hand slider, for instance, white for all three channels, yellow for red and green channels, etc.).

Cheers,

-Michael-