On Tue, Apr 23, 2002 at 09:38:10AM -0400, Tom Trottier wrote:
Dear Tom,
> 1.If 3T/4T full frame sync is at 1/60, wouldn't the curtain travel
> time be ~14ms?
>
> 2.Does it start flashing when the 1st curtain opens and stop when
> the 2nd curtain closes for all speeds shorter than 1/60? This would
> imply a ~15ms time for 1/2000 up to ~27ms for 1/65, or flash
> durations of 1/66 to 1/37, which differs from Olympus specs of 1/50
> to 1/25. At 1/60, since the full frame is available, the flash
> duration could be 1ms or less.
>
> 2.The GN for Super FP at 1/60 is 14.7, not the 28 that could be
> expected. It seems that half the energy is lost using Super FP
> instead of normal OTF.
Exact my thoughts.
>
> 3.The GN must be higher for the OM77 because the sync speed is
> higher and more of the frame is illuminated at any shutter speed. But
> why is it higher at 1/100 (15.6) than for the 4T at 1/60 (14.7)?
Is it possible that the flash recognizes the OM77, and then increases
the frequency of flash emissions? -> different illumination times?
Or is the frequency of flash illumination a fixed value for all FP-operation?
Someone here mentioned, a while ago, it would be about 20kHz?
>
> 4.In auto mode, the shutter speed can vary infinitely, during the
> exposure. Wouldn't this imply that the F280 must preserve enough
> punch for the maximum exposure length, to keep the illumination even,
> an amount not needed if the shutter speed turns out to be 1/2000. In
> manual mode, though, the flash could be concentrated into the minimum
> time, since it's known in advance. So why isn't the GN a little
> different for the two modes?
>
Is there already enough comunication that the camera tells the
flash about the selected shutter speed? -This would be necessary.
Frieder Faig
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