Curtis,
I don't think your observation of the camera's autoexposure at 800 resulting
in 8-10 seconds, and 3 minutes at 400 is a reciprocity falure. That couldn't
be judged until the fill is processed. I think it has a mechanical problem.
Light entering the viewfinder should not impact the exposure where the
initial reading is longer than 1/60. When you exercised the film speed
dial, you may have improved the contacts, but I'd guess a pro job is in
order.
Mickey
----- Original Message -----
From: "John Hudson" <jahudson@xxxxxxx>
To: <olympus@xxxxxxxxxxxxxxx>
Sent: Saturday, December 08, 2001 10:51 AM
Subject: Re: [OM] Help! OM-4T Film Speed problem (I think)
> "Curtis P. Hedman" wrote:
> >
> > I recently tried taking some Christmas lights photos with my 4T, using
ASA
> > 800 film. While taking the shots (in AUTO mode), it seemed like the
> > exposures were too short, and when the film came back, most of the
frames
> > were severely underexposed - except for a few which I shot using the "B"
> > setting and timed myself external to the camera. I then started fiddling
> > with the camera, firing off some shots with lens cap in place (film
loaded,
> > of course). I found that, at the ASA800 setting, the exposures were
running
> > 8-10 seconds at f/2.... shifting to ASA400 resulted in 3 minute
exposures!
> > Thinking the contacts might be dirty I ran the selector back and forth a
few
> > time, and then seemed to get the long exposures at a number of ASA
settings.
> > When I repeated the experiment a day or so later, it was back to short
> > exposures at ASA800, long at ASA400. Seems that the camera doesn't like
the
> > 800 setting! Anything below 400 seems to work OK. Anyone have any
> > suggestions? Could there be a bad spot on the encoder or whatever, or
> > persistent dirty contacts? Are there any other experiments I can try to
> > narrow things done a bit? I did do a 'dark current' check - at ASA 3200
and
> > f/2 (but lens capped), the meter read 1/4 second, which the list archive
s
> > suggests is about right. I did find that even at ASAS25, the longest
> > exposure the camera will deliver is 3 minutes, not the 4 minutes
everyone
> > seems to claim. Do I need to worry about light entering through the
eyepiece
> > during auto exposure, or does the mirror completely block off any stray
> > light during exposure?
> > Lots of questions! Hope someone has some suggestions..... Thanx in
> > advance.
>
> You might be experiencing what is called "reciprocity failure".
> Off-the-shelf-film assumes that exposures will normally be in the range
> from 1/1000 to 1/10 second.
< 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 >
|