Olympus-OM
[Top] [All Lists]

[OM] not quite...

Subject: [OM] not quite...
From: William Sommerwerck <williams@xxxxxxxxxx>
Date: Thu, 24 Sep 1998 20:22:52 -0700
OTF Flash (OM-2n, OM-3Ti, OM-4, OM-4Ti):

1. First curtain begins to open, meter starts accumulating exposure off
of the film and curtain
2. First curtain fully open - Flash fires
3. Meter quenches flash and starts closing the second curtain when
sufficient exposure is measured (or flash fully discharges)
4. Second curtain closed - effective shutter speed 1/60

This isn't the correct sequence. You're combining ambient exposure with
the flash exposure. You definitely DON'T want the shutter closing when
the proper flash exposure has been reached.

In OTF flash mode, the shutter speed has to be 1/60 or slower, or the
flash is inhibited from firing. The sequence would be:

1. First curtain begins to open.
2. First curtain fully open -- flash fires.
3. Meter cell reads light reflected from film plane & circuit integrates
exposure.
4. When full exposure has been reached, flash is quenched.
5. Second shutter is released 1/60 after step #1, whether or not flash
has fired.


Full Synchro Flash (OM-4Ti):

1. First curtain opens, flash begins discharging, meter starts
accumulating exposure off of the film and curtain.
2. When sufficient exposure is achieved, meter triggers the second
curtain to begin closing. Flash continues to fire.
3. Flash stops when the second curtain is closed.

This _is_ correct, with one qualification in Step 2. The flash
contributes relatively little to the exposure (unless the ambient light
is low, in which case, why are you using this mode?).

Note that this is _not_ OTF flash mode. The basic exposure is set by the
camera based on ambient light. The flash isn't involved.

It's important to point out that the camera does not control the level
of the synchro flash in _any_ way. It's fixed. If you're too close to
the subject, you might get excessive fill-in. If you're well back, you
may see little or no fill-in.

< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >


<Prev in Thread] Current Thread [Next in Thread>
Sponsored by Tako
Impressum | Datenschutz