Problem with using a optical slave with a canon flash


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Jul 22, 2003
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#1
As above.

I encountered this problem using a optical slave with my canon flashes.

For the benefit of others, a optical slave unit is a $20-$30 small box unit (about 3cm x 3cm) with a light sensor which u connect to your flash. So when it picks up another flash, it will fire off the flash it is connected to ... supposedly

Ok ... now my problem is ... it only works once. When i put the slave on my 550ex and trigger it off with my built in flash, it only works the first time. Subsequently, it doesn't fire at all. Same problem with the 420ex. Already tried all the possible combination ... M mode, ETTL, Multi ... Only thing i can do after it fires if either switch it off (and on again) or take out the trigger.

Anyone encountered this problem before, or have some information about it ?

p.s. dun tell me to use the 550ex as a master to trigger of my 420ex ... i know that can be done.
 

Jun 12, 2004
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#2
If you trigger the optical slave with either the 550 or the 420, the master unit must be in M mode. ETTL has a preflash which will prematurely trigger the slave.

You cannot use the built in flash as the pre-flash cannot be disabled.

Not sure whether the 550 or 420 needs to be in M when optical slave attached. Worth a try though.
 

Jul 22, 2003
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#3
thanks headlesschook, but its not a pre-flash issue.

AnywayI'm still looking for a solution. I know where the problem lies.

But apparently (from photo.net forum) , most 550/420 flashes will lock up after being triggered by a optical slave unit, hence, it can only fire once. It would be nice if someone knew of any workaround. Apparently Nikon flashes do not have this problem. (no Nikon vs Canon banter please)
 

Jun 12, 2004
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#4
That is indeed a real problem. Will also probably mean that the 550/420 will lock when used on a fully manual camera.
 

loupgarou

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Sep 9, 2003
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optical slave triggers on the level of light, maybe there is a defect in yours (capacity cannot charge properly?) after triggered by a TEST button,can you trigger it again twice?

after triggered by the 550EX, can you use the TEST button to trigger the optical slave?
 

StreetShooter

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#6
darrelchia said:
thanks headlesschook, but its not a pre-flash issue.

AnywayI'm still looking for a solution. I know where the problem lies.

But apparently (from photo.net forum) , most 550/420 flashes will lock up after being triggered by a optical slave unit, hence, it can only fire once. It would be nice if someone knew of any workaround. Apparently Nikon flashes do not have this problem. (no Nikon vs Canon banter please)
Hmmm. Interesting. It does seem to be a documented "feature" acknowledged by Canon.

Your solution is to buy a cheap auto flash. That's another 30 bucks. An even better solution is to get an ST-E2 and take full advantage of ETTL.

Why would you want to use a 550EX with an optical slave? That's like using a 50mm f1.0 lens as a magnifying glass for reading.
 

Jul 22, 2003
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#7
hee ... actually its coz i'm starting to shoot more outdoor fashion/portraiture with another nikon user, and between us, we got 4 flashes. So instead of relying purely on ambient light, we use our flashes to improve lighting conditions, fill shadows, rim lights and stuff. So we use optical slaves in order to trigger off each others flashes, so we can have on flash in our hotshoe + 2 flashes to play with
 

Jul 22, 2003
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#8
loupgarou said:
optical slave triggers on the level of light, maybe there is a defect in yours (capacity cannot charge properly?) after triggered by a TEST button,can you trigger it again twice?

after triggered by the 550EX, can you use the TEST button to trigger the optical slave?
after the flash is triggered by the optical slave, even the test button will fail to fire off the flash. The flash simply locks up, and all the controls do not respond ..(aka HANG) ... :p
 

denniskee

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Oct 26, 2003
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#9
yes, this is a known problem (for EX series flash with optical trigger device) which has been well documented in one of the eos flash web site.

use EZ series and problem solved.
 

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