Actually I learned all this curtain travel verses flash sync the first time it
didn't!!!! What I wanted to know is: Does this flash camera setup give
repeatable
results time after time, or is it a gimmick, similar to the other gimmicks that
Oly
has so adamantly refused to produce like auto focus and built in motor drive on
there
pro models!?
let the flames begin!
Terry
"John A. Lind" wrote:
> At 10:16 6/15/99 , George commented:
> >
> > He asked how *WELL* it worked, not HOW it worked. He was asking about
> >reliability.
> >
> > George S.
> >
>
> If "well" meant "reliability" at 1/1000 compared to "reliability" at
> 1/125th, implying "repeatability" of proper exposure, I'll stand by the (I
> admit lengthy) reply. Understanding the timing of FP-sync answers the
> basic reliability question (as I understood it) and explains how more
> likely problems can arise in using it.
>
> Sequence of events in typical FP-sync at shutter speeds of 1/125th and faster:
> 1. Flash is triggered and begins emitting light (FP mode)
> 2. Opening curtain is released and begins travel
> 3. Closing curtain is released and bgins travel
> 4. Opening curtain completes travel
> 5. Closing curtain completes travel
> 6. Flash ends emitting light (FP mode)
>
> ** This is an entirely different sequence of events from X-sync. **
>
> The curtain speed does not change with changes in shutter speed, only the
> timing between when the opening and closing curtains are released to begin
> their travel. Changes in shutter speed only change the width of the slit
> going across the film gate. If it works reliably at 1/125th it will work
> just as reliably at any faster shutter speed because the delay between
> releasing the opening and closing curtains is shorter.
>
> Most problems using FP-sync at very high shutter speeds are not due to
> reliability. The GN goes down, and therefore the max range of the flash
> decreases, as the shutter speed increases. Problems usually result from
> attempting to use a shutter speed, aperture and subject distance
> combination for which the flash cannot provide enough light causing
> underexposure.
>
> This *presumes* the shutter curtains are adjusted and working properly:
> both curtains traveling at exactly the same, correct speed so the slit is
> the proper width and doesn't widen or narrow during its travel across the
> film gate. If they are not, there will be exposure problems both with and
> without a flash . . . and the problems will appear worse as the shutter
> speed increases.
>
> -- John
>
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