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Old 20th July 2008
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Naughty Nigel Naughty Nigel is offline
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Re: Flash triggering

I may be too late replying, but....

All electronic flashguns charge a large value capacitor to a potential of 300 to 350 or so volts, which is then discharged over a period of a few ÁS through a glass tube containing xenon gas. Indeed, any electronic flashgun (including those in compact cameras) is capable of delivering a fatal electric shock.

The voltage at the flashgun terminals is determined by the triggering circuitry. Older cameras with mechanical flash contacts could safely handle high voltages and currents from simple flashguns without sustaining damage (even though the user was at risk of electrocution). However, modern cameras with solid state flash triggering can only handle low voltages and currents, and may also be sensitive to polarity.

Regarding remote triggering.......
Digital cameras fire their flashguns twice for each exposure.

When the shutter button is pressed, the flashgun fires a short, measured pre-flash to calculate exactly how much flash power is required. This is follwed a few milliseconds later by the main flash. Most remote triggering units are not capable of relaying this information to or from the flashgun, so when the master flash fires its pre-flash, the slave guns fire at full power. Not only does this completely discharge the slave flashguns; it also confuses the exposure system, resulting is severe under-exposure.
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