I've been reading quite a lot on the internet recently about flash trigger voltages and how older flash units often had trigger voltages in excess of 200VDC. This, it was said, would fry the sensitive electronics in a modern digital camera. I've yet to read anything by anyone who has actually experienced this first hand, it all seems to be anecdotal.
So, curiosity tweaked I put new batteries in my collection of flash units and got out my voltmeter.
My old Vivitar 283 measured 110VDC, my little Hanimex CX215 measured 60VDC and a Leica CF came in at 6VDC. So there is truth in the fact that older flash units have higher trigger voltages.
I've read that Canon rate their max trigger voltage at 60VDC, and sure enough my 5D II is still working fine after using the Hanimex on it, likewise I've read that Leica say their cameras are safe upto 600VDC, and my M8 is stil OK after using the Hanimex.
I need to do a bit more research before I chance either the 5D or the M8 with the Vivitar though.
Incidentally, I compared the little Hanimex with the Leica CF, both have a similar GN and have manual or auto (non TTL) settings. Using the settings stated on the back of each unit I took some interior shots on the Leica M8 using both auto and manual settings. The Leica CF was OK on auto but two stops over-exposed on manual. whle the Hanimex was spot on each time, one to the little Hanimex!
Not satisfied with my findings I sent an email to Leica UK asking what are the safe flash trigger voltages for the Leica M8. As usual Leica UK responded quickly with the following:
"A trigger voltage of 24v (max) is considered 'safe' for Leica M digital cameras."
So, from those who should know, if the trigger voltage is greater than 24VDC don't use it on your Leica M digital.