Digital BW, The Print

Concerning levels:

>The Levels adjustment is nothing more than an
>extremely simplified version of the Curves adjustment.

Levels offers a couple of capabilities that distinguish it from Curves tool 
and make it one of the essential Photoshop tools. First, of course, is the 
histogram that lets you see the darkest and lightest values in your data 
and adjust black and white points accordingly. Second is that, when you 
hold down <alt>/<option> while dragging the black and white points up and 
down, Photoshop shows you the actual parts of the image that will be 
clipped. Try it if you don't already know about it. You'll be amazed!

-- Victor Landweber