There are times, when it is very dark, that I'd like to be able to use just the focus assistance on the 580EX.
Have it flash the red lines, so that the lens can focus, but then not fire the flash afterwards.
Is there a way to do that? If so, how?
Reason for wanting to do this: I use several very fast lenses, unfortunately my eyesight isn't quite good enough to be able to manually focus in the dark, quickly or accurately enough.