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woodworker40 Oct 20, 2012 8:40 AM

Vivitar Flash
I have a question, can I use my VivitarAuto Thyristor 550FD flash on my Canon SX40 camera? I know it will fit, but is it safe for the camera?

VTphotog Oct 20, 2012 8:51 AM

Scroll down the page a bit to the Flash(external) forum. there is a thread about voltage limits, with links to places that report on flash trigger voltages. Many older flashes have trigger voltages high enough to potentially damage digital cameras.


JimC Oct 20, 2012 9:52 AM

This thread (a Sticky at the top of the "Flash (External)" Forum we added after Brian (Vtphoto) suggested one about Trigger Voltages:

It has a link to this page showing some Trigger Voltages measured by users:

It looks like that model is labeled as "Your Call" based on what others measured (as some measured around 10 volts, which is higher than Canon recommends for their hotshot, which is reported to be 6 volts). See the discussion at the top of that page about Canon's comments about trigger voltage.

Your call, but I'd probably measure your specific flash and see what it's trigger voltage is (it may be lower or higher than other specific flashes like it, as sometimes you see different components used due to revisions over time to a given flash model that impact trigger voltage). See how to do that here (basically, with the Flash charged up, use a digital voltmeter and measure the voltage between the center pin and the metal contact you'll see on the outside of the Flash hotshoe).

Personally, if it was less than 10 volts, I'd probably risk using it (especially if it was pretty close to the 6 Volts Canon specifies). But, it's your call (as damage from trigger voltages that are too high for a camera's design can be cumulative). You'll see a lot of arguments both ways (what the Canon models are really capable of using, as some users feel Canon is just being overly cautious in their responses, as you can see in some of the discussions about it around).

Ozzie_Traveller Oct 20, 2012 4:53 PM

G'day ww40

On the other hand, you can google to locate plenty of non-canon-brand flashes designed for digital cameras - there's plenty in the $50-$75 range if you look for them > a lot depends upon how automatic you want / need the flash to be

Regards, Phil

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