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Re: [OM] OM2+flash

Subject: Re: [OM] OM2+flash
From: Jim Brokaw <jbrokaw@xxxxxxxxxxx>
Date: Wed, 23 Jan 2002 14:04:19 -0800
on 1/23/02 10:48 AM, M. Royer at royer007@xxxxxxxxx wrote:

> I know this sounds really dumb, but what IS the
> difference between all these different syncs. What
> exactly is FP sync? How is it any diffrent from X and
> what makes X so special. Pardon my ignorance. I've
> only ever used T-flashes
> 
> Mark Lloyd
> 

Flash sybc is designed to make sure that the shutter is fully opened when
the maximum level of flash light is being 'flashed' onto the subject. With
an electronic flash, the light output is nearly instantaneous, so the X-sync
triggers the flash as soon as the first shutter curtain is fully open. There
is also a variation (second curtain sync) that triggers the flash just
before the second shutter curtain starts to close.

With flashbulbs there is an actual burning of fine wire (magnesium or
zirconium in a pure-oxygen atmosphere if I remember right) and this takes
some time to reach peak light output. So the flashbulb is ignited a few
milliseconds *before* the first shutter curtain opens, allowing the bulb to
be at full light output when the film is exposed. Because an electronic
flash's light output is very brief, if on FP sync the light output has
flashed and gone before the shutter even opens.

With FP flash bulbs the light output stays steady for some relatively long
period of time, so you can use higher shutter speeds (which are made in
focal plane shutters by moving a slit across the film) as the light output
will be relatively constant during the period that the shutter curtains slit
is moving across the film. The F-280 flash mimics this long-duration light
output by doing many overlapping electronic discharges.
-- 

Jim Brokaw
OM-1's, -2's, -4's, (no -3's yet) and no OM-oney... 


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