Michael Darnton , Sep 02, 2004; 08:08 a.m.
The most versatile tool is curves, best used as a layer (layer/new adjustment layer/curves). With that you can adjust color, contrast, AND local contrast in various tonal ranges.
To do correction the way the raw converter does it, use the three eyedropper buttons--click on the right one, find the area in the photo you want to be pure white, and click on that. Then click on the left button, and click on an area you want to be pure black. Then, if you have a true grey somewhere in the photo (but it's got to be true) you can use the middle button and click on the grey. To cancel everything, press ALT, and the "cancel" button becomes "reset" to start over.
This is the simple way, but if you read up on it, there are many, many other things you can do with curves. For instance, to darken or lighten without messing with white or black, click on the center of the diagonal line and drag it up or down. By putting s-curves in the line, you can change even more stuff.
Curves is essentially a more complex and more versatile version of levels, which really is a crude tool, when it comes down to it, except for very simple corrections, but the eyedroppers in the levels box work the same, as does the midpoint slider compare with pushing the center of the curve around. Levels won't let you adjust local problems by putting twists in the curve, though.