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05-17-2013, 03:36 AM   #16
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QuoteOriginally posted by Lowell Goudge Quote

Pretty good explanation, but there needs to be a correction.

TTL does read the light reflected off the sensor (or film) but does not use a preflash. It terminates the flash much like AUTO flash units, but the exposure continues until the end of the shutter period, leading potentially to over exposure in strong background light

P-TTL uses the cameras built in metering in the prism taking both ambient light and pre-flash light through the cameras normal metering, and then calculates the flash duration required in addition to the ambient to get the exposure.

TTL is a reactive process, P-TTL is a predictive process
Hi Lowell

That's why I said that TTL is good for fill in flash, often you want to use settings that remove the ambient and record just (or mostly) the flash component which is where Manual flash can score.


05-17-2013, 07:58 AM   #17
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An auto flash should work cross brands, right? So long as the camera uses a standard hotshoe.

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