In a message dated 6/15/99 3:26:20 PM EST, jlind@xxxxxxxxxxx writes:
<<
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 >>
WOW ! ANOTHER record reply to a question that WASN'T ASKED !!! He
asked about *reliability* why must you assume he meant something else?!
NOBODY, not him, nor I asked for a lesson in "FP Flash 101"
I'll bet you never cease to amaze yourself, huh?
George S.
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