Thanks, John. I've been around *just* long enough to have used FP flash
bulbs (not cubes, etc.) for a couple of years as a kid when they were still
available and not considered collectibles. And I understand how sync
differs; besides FP and X I seem to recall an "M". But I wasn't sure how
units like the F280 operated, having never seen one. I didn't know whether
this flash emits a long, continuous flash or a series of relatively lower
intensity strobe bursts.
Purely out of ignorance and speculation I'm wondering whether a conventional
electronic flash unit can be modified to emit a single burst of long
duration, or whether this simply isn't feasible. I can imagine this would
wear out the unit and batteries pretty quickly, but for certain photo uses
it'd be worthwhile.
Lex
===
From: "John A. Lind" <jlind@xxxxxxxxxxx>
Subject: Re: [OM] Flash sync question
Date: Mon, 28 Aug 2000 20:20:27 +0000
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.
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