I've been using cheap Chinese radio slaves for a couple of years on
Alien Bees, T-32's and Sunpak 422D's. None of them comes very close to
having the range stated in the specs but, within their limited range
they seem to work well and I've been using them without problems. I
recently acquired a Canyon 540EZ because, while it doesn't do auto
anything on a Canyon digital, it has the most powerful autofocus assist
light that Canyon had ever produced (15 meter range).
While shooting with the slaves and Alien Bees recently I noticed that I
wasn't getting the 1/200 sec flash sync speed of the 5D and had to drop
down to 1/160 to avoid a bit of shutter curtain shadow. To see if that
was due to the slaves or the Bees I grabbed the 540EZ and attached one
of the slaves to it. I ultimately determined that the sync problem is
clearly due to a short delay imposed by the slaves but, along the way
and much to my surprise, I discovered that the slaves (all 5 of them of
2 different makes) almost don't work at all with the 540EZ. Whether
they fire it or not seems to be a random event with perhaps (on average)
one flash every 15 times the slave is triggered. In other words, unusable.
I first suspected a bad connection but soon discovered that I could
remove the radio slave and trigger the same setup manually 100% of the
time. Also, if I substitute one of my Sunpak 422D's in the same hot
shoe setup all 5 different slaves units will fire it 100% of the time.
Is this somehow related to the trigger voltage of the flash unit? My
T-32's and Sunpak 422D's are all in the 10-12 volt range. I don't know
the exact trigger voltage of the Alien Bees other than the spec says
"less than 6 volts". The Canyon 540EZ, on the other hand, is about 3.4
volts with alkalines and about 3.7 volts on the high voltage battery pack.
It's not a big deal to me since I have plenty of other flash units to
use should I decide to take the flash off-camera but I am intensely
curious as to why this flash won't trigger with a slave that fires
everything else.
Chuck Norcutt
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