The "M sync" and "F sync" stands for "Medium" and "Fast" respectively. It
refers to the average time for the flashbulb to reach full output, the "F"
bulbs getting there faster than the "F" bulbs and thus requiring different
delays in the prefire (particularly with leaf shutters) before opening the
shutter. "M" bulbs require about 20ms (similar to the "FP" bulbs). "F"
bulbs require about 5ms, making them usable with "X sync" on many cameras
if your sutter speed is 1/30th or slower (1/30th second = 33ms). As long
as the shutter is still open during nearly all of the full output it will work.
-- John
At 00:12 8/30/00 , Gregg wrote:
>Lex,
>
>How about some flash powder. That would have the long duration you
>need. I would certainly keep it outdoors though.
>
>I believe the difference between the FP bulbs and the M bulbs is how
>fast they light and how long they stay lit. The Ms are for a leaf
>shutter.
>
>Gregg
>
>
>----- Original Message -----
>From: "Lex Jenkins" <lexjenkins@xxxxxxxxxxx>
>To: <olympus@xxxxxxxxxxxxxxx>
>Sent: Monday, August 28, 2000 11:56 PM
>Subject: Re: [OM] Flash sync question
>
>
>| 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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