Dear C.H.Ling
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.
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)?
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?
Has anyone tested this on a bench?
tOM
On Tuesday, April 23, 2002 at 15:22, C.H.Ling
<olympus@xxxxxxxxxxxxxxx>
wrote re "Re: [OM] even more about the F280" saying:
> Hi Tom,
>
> Yes, the OM shutter curtain travel speed is fixed at around 11ms(?).
> But you and many people ignored there is a second curtain. At 1/60s,
> the 2nd curtain will only start when 1st curtain finish. The total
> time could be around 22ms. Only at 1/2000s the two curtains action
> time can be close to 11ms. The timing is just provide you a rough
> idea, actually there could be 1 or 2ms between the 1st and 2nd curtain
> at 1/60s and at 1/2000s there is a slit between the 1st and 2nd
> curtain that could take 1 or 2ms to run.
>
> C.H.Ling
>
> Tom@xxxxxxxxxxxxx wrote:
> >
> > On what speeds does the F280 change it's duration and why?
> > It seems to me the curtain slot always takes 1/60 at 1/60 and faster
> > speeds, and at slower speeds, the flash could be done in 1/60 without any
> > problem.
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