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ScubaRoy
30th July 2009, 06:36 PM
I was playing about today using a slave flash to even out the lighting on some stuff I am selling on ebay.

The slave flash has a power selector that is calibrated in f stops. When I select f11 on the slave (the most power?) the slave doesn't fire. It will only fire at f5.6 and below. I am testing if it fires by pointing the slave towards the camera, when it fires then it is pretty obvious.

I'm using an E520 and FL50 and have tried changing the shutter speed as low as 1/60th just in case the slave is actually firing but after the shutter has closed. I would have thought that the lower the power on the strobe then the shorter the flash so the more powerful setting should show up more.

I have also tried both modes on the slave just to eliminate any pre-flashes spuriously triggering it.

Any ideas on what else i could try?

Roy

photo_owl
30th July 2009, 06:41 PM
what mode are you using the main flash in?

are you sure you are using the slave in an M mode and not an A one?

ScubaRoy
30th July 2009, 06:53 PM
The main flash is in TTL mode.

The slave is purely a manual slave. It's actually an underwater slave that I have so thought would put to use above water. It has always worked perfectly underwater although it is triggered using a fiber optic cable rather than just incident light as I am trying at the moment.

Roy

photo_owl
30th July 2009, 08:31 PM
the pre flash from the main will trigger the slave and I wouldn't rely on 1/60th to bring it into the leaf movement.

from memory the preflash is 1/100th prior to the flash exposure, and increasing the output from the slave will, on most models, increase it's duration (from about 1/20,000th to maybe 1/1000th) so that shouldn't affect the equation - which leads me to confusion about the impact of the aperture setting impact you reference.

an obvious first step would be to try auto instead of ttl auto - and see where things are from that change (which ensures a sync between the flash and slave)

ScubaRoy
30th July 2009, 09:07 PM
I'm puzzled as well as to why the slave power settings should make any difference. I'll have another play with things tomorrow and see if I can find some combination of setings that work reliably.