![]() ![]() A "switch" inside the camera provides closure of a circuit when the shutter fires, causing the flash to fire at the appropriate time. īasically the flash, when charged, has a voltage across its terminals. The reasons are discussed in great detail at m/photo/strobeVolts.html. 1/30,000 the sec flash duration as the sole illuminant.īrian, using an old flash with a modern day DSLR can be very risky (as Perfect 10 pointed out). I will try to attach a couple of jpegs that show one of my microscopes set up with a Canon EOS 60D using Live View and with a Vivitar 283 flash firing through the light path the other shot is a typical subject a rotifer (approx 0.5 mm total length) feeding by whirling the head mounted cilia to draw in microscopical algae etc. ![]() To my knowledge the Canon EOS T3i Rebel/ 600D is the first of the company's Live View models that deliberately prevents non-Canon flash units from firing when the camera is in Live View mode - and it is a work-round to this specific omission that I am trying to find. Vivitar 283 flash units are probably unique in that the flash duration is easily adjusted using a wired remote control unit and many microscopists, amateur and professional, swear by the powerful 283 units. Framing and photographing them requires both a rapid hand and eye response and a very brief flash duration. Using the open flash technique would not work for me: I use flash to freeze the high-speed motion of protozoa cilia and other such free-living biological specimens. I use Wein and Paramount 'safe sync' devices to obviate the problem. ![]() I should mention that I have been using various Canon dslr cameras with Vivitar 283 flash units for the past six or seven years and am well aware of the trigger voltage hazard the 'old style' flash units pose to our modern electronically packed dslrs. Thanks PaulB, Xarqi and SnapFire for your speedy reponses. Have you checked the trigger voltages of the 600D and the Vivitar flash first though? If the 600D requires only the trigger voltage that Canon EX guns supply then a higher trigger voltage could fry the flash circuits in the camera. ![]() It could be to do with the different trigger voltages of non-Canon flashes. ![]()
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