Help: problem with 420ex in slave mode

Recently, my canon 420ex flash has been firing approximately one second after the master (either 580EXII or MX-14) has fired. Slave and flash are set to channel 1 and group C. what am I doing wrong? Thanks in advance

Hopefully someone will reply, I have the same problem.

My 550ex starts to do that as slave to 580ex sometimes - usually after working fine for 20-40 shots - definitely couldnt be overheating, as i dont shoot that fast...... hopefully we can figure this one out.

Something related to second curtain flash, maybe?

alduin wrote in post #14225267
Something related to second curtain flash, maybe?

Nope ! double checked that already.

Everything will work just fine initially with perfect wireless ETTL exposures, and the later the slave will start to behave erratic and fire approx 0 .5 to 1 second later - and the pulse seems kind of weak - but if i set it to manual, it fires normal. (The batteries are normal, and sometimes even when connected to the canon power pack - so couldn't be weak batteries either)

starlights wrote in post #14225427
Nope ! double checked that already.

Everything will work just fine initially with perfect wireless ETTL exposures, and the later the slave will start to behave erratic and fire approx 0 .5 to 1 second later - and the pulse seems kind of weak - but if i set it to manual, it fires normal. (The batteries are normal, and sometimes even when connected to the canon power pack - so couldn't be weak batteries either)

Do you mean setting the camera to manual mode? The 420EX has no manual mode.

msowsun wrote in post #14225577
Do you mean setting the camera to manual mode? The 420EX has no manual mode.

starlights wrote in post #14225254
My 550ex starts to do that as slave to 580ex sometimes - usually after working fine for 20-40 shots - definitely couldnt be overheating, as i dont shoot that fast...... hopefully we can figure this one out.

Sorry about the confusion ( though this thread was started by OP for 420Ex, I am talking about using 550EX as slave to 580EX master) - since i am getting the same irratic behavior from my 550ex in wireless ettl mode as OP seems to be experiencing with his 420EX.....

The only thing I can think of is that the Canon wireless system incorporates a test function that will fire each slave with a delay just as you describe. Maybe it is the master that is causing the problem?

Gah, yes! Put it in group B and see if the delay is a little shorter.