Thus spake ChrisPlatt:
> The original Olympus OM-2 has a similar specification but reportedly can make
> autoexposures several times that length. Interestingly the later "improved" OM-2n
> has an absolute limit of 2 minutes for autoexposures.
I am wondering about this myself. I found online a claim that someone's longest exposure was 15 minutes.
The laws of reciprocity are also bothering me and they look to be a real show-stopper. I just looked it up in the
fact sheet for Ilford's Delta 100: A measured exposure of 30 seconds does in fact require an actual exposure of 150 seconds, or so they claim. That's more than two stops off! Other Ilfords are in the same range. So even if an EC of 2x works, this would not be enough for even longer exposures. T-MAX 100 only appears to require +1 stop of light but I'd be very unhappy to part with my beloved Ilford film.
Meanwhile, I just stepped out onto my roof here and tried my Seconic light meter. It's hopelessly inadequate, of course, and reads nothing. I am hearing good things about the Gossen Luna meters, and used specimens are cheap. So there's maybe a fallback.
Cheers,
Tassilo