Another way to create contrast, and what I do all the time, is to run a job twice. If part of your artwork is 100% black and some of it is 50% black, like gray, you can run the black first, then run the gray. On a second run, run the black at 100% power and (let’s say 60-70 speed). Next, run the gray at 50% power and 80 speed. The gray would be lighter if you did it all in one run, but this way you have control. You could use color mapping but still would not have the same control; what I like about this method is if the gray is not quite dark enough, you can still run it again.
-Doug Green, Express Yourself Austin