580EX & 420EX Question

I have a 580EX and 420EX, I want to have the 580 fire the 420 without the 580 actually firing. I have searched the manual and found nothing.

I can get both to fire but I just want the 420 to fire and not the 580.

Page 36 in your 580ex manual.

-580 on hotshoe of camera, set to master
-420 off camera set to slave
-Set both to same channel.
-Set to different groups if using ratios (whole other topic)
-On the 580 you should see a picture of the flash just left of the CH box. Hit the ZOOM button until you see the flash where it looks like it's emitting a flash on the screen. The Screen should say ON or OFF. If it says ON, turn the main dial on the flash until it says OFF.

Proceed with your picture taking. You will still see a flash emit from the 580. This is actually the signal to the 420. It will not, or should not, affect you picture. It actually occurs before the shutter release.

Take the flashes and place them infront of a mirror, take a picture of both firing in master/slave mode, you will see the master 580 always flash even it is turned off.