This is defined as "FP" flash sync. It was originally done with special
long duration flash bulbs such as the the 26, the long duration cousin of
the famous press 25. To sync correctly the camera had to have an "FP" sync
position which would prefire the flash bulb about 20ms before releasing the
leading curtain so that the bulb would be up to full output before anything
opened. The duration had to be long enough for the trailing curtain to
completely close; standard flash bulbs were not long enough in duration.
In today's world of electronic strobes, the long duration is accomplished
by a very rapid series of light bursts consuming the entire output. As
with flash bulbs, an electronic FP sync must prefire the flash just before
the leading curtain opens and its duration of very rapid bursts must
continue until the trailing curtain closes. This is how the F280 with an
OM-3ti or OM-4ti works in "FP" mode. The trick would not so much be
getting an extended duration; electronics could be added to a flash unit to
do that. The trick would be prefiring prior to the leading curtain
release. On any but the OM-1[n] with the "FP" position (set up for flash
bulbs, not electronic), you would have to somehow modify the sync to
prefire the flash unit. Perhaps an OM-3ti or OM-4ti could be adapted; I'm
totally unsure of that.
That would be the daunting task. The X-sync works by firing the flash
after the leading curtain has fully traveled. It presumes you will be set
to the X-sync shutter speed which has the opening curtain fully open for a
short time before the trailing curtain is released to close the shutter.
It means you would have to monkey with the sync timing considerably and fix
things so that the flash sync fires the flash just *before* the opening
curtain is released.
-- John
At 00:27 8/29/00 , Lex asked:
>Does anyone make a flash (clip-on or studio) that allows synchronization
>beyond the usual limit for a camera? As I understand it, this is a factor
>of flash duration. If a flash duration is long enough, one can in effect
>extend synchronization beyond that designed for a particular focal plane
>shutter mechanism. Any thoughts?
>
>Lex
>===
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