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Photography Question 
Ellie van Rooyen
BetterPhoto Member Since: 2/15/2004
 

Flashes


Hi there!
I have an old flash, which my father used on his old film SLR. It still works and is in perfect condition, and I was wondering if I could use it on my Canon EOS XT digital SLR camera, it works, Iíve tested it, but the thing is, Iíve heard some people saying that you will damage your digital if you use old flashes on it? But then other people say its bull. Can someone please give me a decisive answer, as Iím itching to start with flash photography? Should I empty out my pockets for a proper Canon / Sigma flash? Or is it safe to use the old one?


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12/1/2005 12:00:10 AM

 
Jon Close
BetterPhoto Member Since: 5/18/2000
  Many older flash units create high voltage (as much as several hundred volts) across the hot shoe terminals when fired. This was not a problem for older manual cameras that had a simple trigger circuit separate from the camera's meter and other functions. For modern electronic cameras that have TTL metering communication with the flash, these high trigger voltages can damage a camera's electronics.

The Rebel and Elan EOS film SLRs are generally limited to flashes with trigger voltage ~8v or less. The EOS Digital Rebels and 10D/20D are a bit more robust, but the manuals do not specify a safe voltage limit for the hotshoe. The manual for the Digital Rebel XT has just the warning "Do not attach a high-voltage flash unit on the camera's hot shoe." (p. 102)

To be safe, you should test the trigger voltage of your old flash. Testing procedure and a database of tested flash units is available at http://www.botzilla.com/photo/strobeVolts.html. If the flash has a high trigger voltage, it can be safely used with an adapter that blocks high voltage from the camera, such as the Wein Safe Sync.


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12/1/2005 6:27:45 AM

 
Ellie van Rooyen
BetterPhoto Member Since: 2/15/2004
  Thanx Jon! You were of great help to me, great article as well! Can I just ask you one last question; after reading the article, I decided to be "better safe than sorry". What do you think about the Sigma 580?


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12/1/2005 9:58:59 PM

 
Jon Close
BetterPhoto Member Since: 5/18/2000
  I haven't used them, but the Sigma flashes seem to be a popular alternative to Canon's speedlights. There are 2 similar Sigma models: EF 500 DG ST and EF 500 DG Super. The ST has more limited function. It is similar to the Canon 420EX, but allows setting the output manually (full and 1/16). The Super is full featured, emulating the Canon 550EX, but not quite as powerful. The AF assist light on the Canon speedlights better match the focus sensors of the EOS cameras. The Sigma's AF assist is targeted for the center sensor only.

See http://www.sigma-photo.com/flashes/flashes_flashes.asp for descriptions and a chart of feature compatibilities.


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12/2/2005 5:20:45 AM

 
Ellie van Rooyen
BetterPhoto Member Since: 2/15/2004
  Thanx a lot for your help, really appreciate it!


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12/2/2005 5:33:52 AM

 
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