Delay between master and slave 580 ex IIs

[ksreid]

While exploring wireless flash with my two 580 ex IIs, I noticed when I test-popped the master, there was a delay in the slave firing. This test was run while the master was not mounted on my camera and the slave's sensor was pointed in the direction of the master's flash.  The master was set to the "on" position, so I wasn't attempting to have it send out a "reading" flash. Any suggestions?

[Skirball · Accepted solution]

So you tested it by triggering a test pop on the master by hand (instead of having the camera trigger it)?  Or are you using a wire/trigger of some sort?

If the former, why not put the master on-camera and test it out?

[ksreid]

Thanks, Skirball. Not real sure why putting the master flash on the camera worked, but it did. Obviously has something to do with the E-TTL. I think I'll play around with putting both flashes in Manual mode and see if that makes a difference with regards to the delay.

[TCampbell]

There is a mode where you can use a flash as a remote trigger (off camera).  When this is done the delay is intentional.

Canon wants to be certain that the light from the off-camera flash does not interfere with the shot -- this way the illumination is provided only by either on-camera flash OR flashes designated to work as slaves.

On the 600EX-RT it's also possible to use a flash to remotely control one camera from another camera.  This has the same delay behavior (so that the light of one camera -- which may be mobile -- is not interfering with the light of the remote camera.)

BTW, I don't *think* the 580EX II supports remote camera triggering, but I may be wrong.  I know the 600's support it (I've done it.)