Can I use Vivitar 550FD flash on Canon 40D

[mikinla]

I had seen someone memtioned that Vivtar 550FD flash
can be used on Canon 20D. Can it be used on Canon 40D?
If someone knows, please help.

[ziggy53]

I had seen someone memtioned that Vivtar 550FD flash
can be used on Canon 20D. Can it be used on Canon 40D?
If someone knows, please help.

Mikinla, welcome to the Digital Grin. :clap

The problem with old flashes and digital cameras is that some older flashes have a very high "trigger voltage".

To check a flash unit for trigger voltage you can test it for yourself using the method described here:

http://www.botzilla.com/photo/g1strobe.html

To see if that particular flash has been tested by others see here:

http://www.botzilla.com/photo/strobeVolts.html

If you want to isolate your camera from potentially dangerous trigger voltage from vitually any flash, use a Wein SafeSync like:

http://www.bhphotovideo.com/c/product/245292-REG/Wein_W990560_Safe_Sync_Hot_Shoe_to.html