On Sun, 27 Dec 1998 22:56:29 +1100, Frank Ernens <fgernens@xxxxxxxxxxxxxxx>
jammed all night, and by sunrise was overheard remarking:
> Wayne Harridge wrote:
> > I saw somewhere (the FAQ maybe) that the maximum exposure time for
> > the OM-2N is 2 minutes, however I tested my OM-2N and found that the shutter
> > consistently closed after 3 min 48 sec with a body cap attached. Is this
> > normal or is my OM-2N faulty.
> I don't think so. My OM2N also goes past 2 minutes, but exposures made
> with it look correct down to 10-20s (as long as I have tried).
> You can end the exposure by moving the switch from AUTO to OFF.
I suspect the 2 minute time is something related to the sensitivity of
the photodiodes -- they probably can't spec it perfectly, but at a
constant light level less than one that would yield a 2 minute time,
they can't guarantee the photodiodes detect any light, so the system
won't necessarily every terminate its exposure.
> The 2 minutes may well be regulated by a capacitor, being before
> the days of embedded CPUs, and some types of caps alter their
> values with age.
This is certainly possible -- electrolyte can decay with time, depending
on the type of cap used.
However, on the long exposure side, you're going to run into resoprosity
failure, the film's sensitivity is no longer linear. SInce this varies
entirely by film, the camera can't do anything about it (maybe a modern
one could if full data about the film type were uploaded to its computer,
but that hasn't happend yet).
--
Dave Haynie | V.P. Technology, Met@box Infonet, AG | http://www.metabox.de
Be Dev #2024 | NB851 Powered! | Amiga 2000, 3000, 4000, PIOS One
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