AlunFoto wrote:
In the AF-540FGZ manual it says there is an absolute minimum usable
distance in P-TTL (0.7 m). I always thought that was because the flash
was unable to quench its output fast enough to operate at shorter
distances. I thought so because quenching the blink was how the old
TTL system worked.
My idea too.
Then, today I took the flash off-camera and began
experimenting. To my surprise, the shots where the flash was closer
than 70 cm from the subject became underexposed, not overexposed. It
got worse the closer I held the flash.
The only explanation I have come up with is that the power used for
preflash must be constant, and too strong to let the camera meter
accurately at distances shorter than 70 cm.
Maybe this was obvious to everyone but me. So, eureka or d'oh?
Good to know, thanks Jostein.
Dario
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