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What's with "D" flashes for digital cameras?


nikon geek

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Flash metering on a film camera records the light reflected off the film during the exposure. A digital sensor doesn't reflect light in such a convenient and consistent fashion.

 

Consequently digital cameras need a different strategy to measure flash. One common solution is to fire a small pre-flash an instant before the mirror raises, this pre-flash is used for exposure measurement only and doesn't contribute towards illuminating the shot.

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Though I may be wrong, I think what you're referring to as "D" flashes are actually "D" for "distance"-- D lenses (for Nikon, at least) transmit distance information to the flash via the camera body, and since flash exposure is determined by distance and f-stop, the focusing distance is used to calculate the correct flash exposure.
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Let me clarify... What I am actually referring to are what Nikon would call "DX" flashes or what Quantum would call the new "T4D". Again, they are flashes that are specifically designed for digital cameras. (I realize what the "D" lenses are.) The pre-flash referred to in the first response is something that Nikon already has on their flashes for the film cameras (i.e. the sb-28, sb-80). Anyone else know anything else about this subject???
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Nathan, I can't comment on current Nikon technology as I use Canon, where the pre-flash distinction is the key one. I do however use T4d's, and there the same thing applies, pre-flash TTL exposure measurement is the chief difference between digital and non-digital flash units. Of course you can always use a non-digital flash on a digital camera, you just use "manual" or "auto" exposure measurement and forego the "TTL" function.
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