opacity refers to the total amount that can be drawn in one strokeif it's set to 50% for example, no matter how long you hold down the airbrush, you will only achieve 50% coverage :) (i never use it that way, in fact i've gone back to PS6 because it has a better airbrush)
(
tweaknik,
Sat 17 Jul 2004, 3:15,
archived)