I was just thinking about what happens when you take long exposures, and I
was wondering something:
Say I'm taking a photo in a dark room; I set the aperture, focus, press the
shutter release.
The OM sits there adding up light until it thinks it's had enough, and then
closes the shutter again. Let's say it took 15 seconds for this to happen,
and that I'm using Ilford HP5+ film. According to the Ilford datasheet, I
should actually have exposed the film for about 55 seconds instead -- that's
a fairly large difference.
How do I get around this? It seems like there's two approaches here:
1. Get a very sensitive light meter that'll tell me what's going on; I
don't know how much of a meter I'd need to work in that little light, but I
suspect a reasonably decent one -- the selenium cell one I have stops being
useful as soon as it gets gloomy..
2. Take the first shot, time it by hand, look up the real time on the
datasheet, and then take a second exposure on Bulb to give the correct
amount of time.
Neither of these is exactly convenient; one way I need a meter, the other
way I take two shots for every one I wanted to take, and have to fiddle
around timing the shutter the first time through.
Is there some way to solve this problem? Presumably the camera doesn't have
built-in reciprocity failure compensation.. (hm, that seems like something
you _could_ usefully have as an added feature on a wunderbrick, for once)
-- dan
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