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RE: [OM] F280 vs 3rd party Fill Flash

Subject: RE: [OM] F280 vs 3rd party Fill Flash
From: "Brian P. Huber" <bphuber@xxxxxxxxxx>
Date: Mon, 14 Jun 1999 12:05:14 -0400
Barry,
In re-reading your question, I see I left out some additional info that you
may need.
That relates to the shutter of the camera.  OM focal plane shutters at
speeds 1/60 and slower are open the entire frame.  In other words, the first
curtain is entirely pulled across before the second curtain has started
"chasing" it.
At speeds faster than 1/60, both curtains are moving across the frame at the
same time.  What is changing exposure is the width of the opening between
the curtains.  At 1/1000, the width is very narrow.
 We might see this at 1/60: ]      [
At 1/250 we might see:       ]   [
and at 1/1000 see:              ][
The area between the ][ is the exposed frame (hope formatting doesn't screw
this up!).  Varying the width of the curtains doesn't change things much
when we're dealing with a constant source of light (sun, photofloods).  But
with electronic flash and speeds 1/1000 or faster, problems start.  Even the
MONSTER flashes have flash speeds of ~1/400 sec.
When a flash fires and shutter speed is faster than 1/60, only the portion
open in the slit will be exposed.  Since the flash exposure is less than the
shutter speed, only the slit is exposed to flash.  That's why you'll see
only a partially exposed frame when shutter speed is set too high and flash
is used in dark area.

So how does N*k*n and others get flash sync shutter speeds at 1/125 and
higher?  Their shutters run vertically rather than horizontally (shorter
distance) so the shutter can stay open longer.

Brian P. Huber

bphuber@xxxxxxxxxx
Troy, OH


-----Original Message-----
From:   owner-olympus@xxxxxxxxxxxxxxx [mailto:owner-olympus@xxxxxxxxxxxxxxx]
On Behalf Of Barry B. Bean
Sent:   Monday, June 14, 1999 9:31 AM
To:     Zuiko-holics Anonymous
Subject:        [OM] F280 vs 3rd party Fill Flash

I'm waiting on my F280 manual to arrive from Olympus, but in the
meantime, maybe someone can tell me the difference between a synced
F280 flash at, say, 1/250 and my 3rd party (Kalimar) 1/16 fill flash
at the same speed? Presumably, since there's enough light for the
camera to be shooting at 1/250, both flashes are fulfilling the same
function, right? And either way, my Om-4T will be using its OTF
metering and close the shutter when enough light has registered,
right?

On another note, I've gotten so comfortable with my tilting flash
head that the F280's fixed angle head is a decided handicap. I wish
Olympus had designed their flash with a tilt head.

BBB
-
B.B. Bean - Have horn, will travel                              
bbbean@xxxxxxxxxxxxxx
Peach Orchard, MO                                       
http://www.beancotton.com/bbbean.shtml


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