David wrote:
> It's really based on measured EV rating, I think, rather than time. So
> you'll get longer exposures with slower film, at least within some
> limits, and of course, this doesn't take into account reciprocity
> failure. Here's the specs I have:
>
> OM-2 60sec @ ASA100 (approx -5 EV)
> OM-2n 120sec @ ASA100 (approx -6 EV)
> OM-2sp 120sec @ ASA100 (approx -6 EV)
> OM-4 240sec @ ASA100 (approx -7 EV)
> OM-4Ti 240sec @ ASA100 (approx -7 EV)
I did some tests with my OM-2n and got the following results using a body
cap (ie. no light):
ISO 100 3 Min 48 Sec
ISO 1600 3 Min 44 Sec
ISO 25 3 Min 48 Sec
The thing to keep in mind is that even though it gives you a long exposure
there is no guarantee of the accuracy. My guess is that with very low light
levels, leakage currents within the exposure/timing circuit probably have a
major contribution in determining the actual length of the exposure.
Perhaps the "spec" is the longest exposure for which the exposure/timing
circuits are reasonably accurate.
>
> None of the amature series OMs need apply (they're around around 0EV,
> maybe 2sec at ASA100).
I got the following results with my OM-10
ISO 100 8 Sec
ISO 1600 <2 Sec
ISO 25 26 Sec
Wayne Harridge
Ivanhoe, Victoria, Australia
http://www.geocities.com/Paris/Louvre/6152/
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