In the previous post, I discussed the features required for a flash to be suitable for mounting on an EOS digital SLR camera to trigger caving slave units attached to other flashes. A quick summary is that we are looking for a flash with a trigger contact voltage of no more than 6V, and which does not fire a pre-flash before the main burst of light used to take the photograph. The pre-flash is a feature of the E-TTL mode of many dedicated Canon compatible flashes for digital camera models. We are also looking for something cheap to do the job, rather than spending £150+ (550EX prices on Ebay) on a high end Canon EX speedlight which allows you to turn off the E-TTL mode. Of course if you already own a 550EX or 580EX Canon speedlight then this should work for you as long as you turn off the E-TTL mode.
We have found that as a general rule, any Canon EOS compatible TTL flash should be OK. I cannot promise all models will work of course, but here are some which I have actually used so can be certain they will work:
Vivitar 736AFC - Can be got very cheaply on Ebay when they do appear
Metz 40MZ series flashes with Canon hotshoe SCA adapters
Metz 45 series hammer head flashes with Canon SCA modules
These last two Metz models are not so cheap, but are excellent off camera flashes too, being powerful but taking AA batteries, so easy to carry spare sets.
In theory any manual cheap flash with no fancy dedicated features should also work, as long as the trigger voltage does not exceed what your camera can handle. On Canon EOS digital cameras, that is just 6V. The older TTL models of Canon speedlights (the EZ series) should be a safe bet, but again I have not been able to test any of these myself. You could also use a device to protect the camera from the flash trigger voltage (e.g. a Wein Safe Sync). The following link gives some useful information on trigger voltages for Canon cameras and the possible dangers to your camera. It also talks about flash isolators:
http://photonotes.org/articles/eos-flash/index2.html#trigger
There is a very useful list of flash trigger voltages online which may help you find something that works for you:
http://www.botzilla.com/photo/strobeVolts.html
Other options include disabling the E-TTL feature on E-TTL flashes which I have not tried, but I found these details here:
http://photonotes.org/articles/eos-flash/#disableettl
Wednesday 1 July 2009
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