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[OM] An observation and a little theory...

Subject: [OM] An observation and a little theory...
From: Olaf Greve <Ogreve@xxxxxxx>
Date: Sun, 31 Oct 1999 12:45:50 +0100
Hey guys,

Coming from a (computer science) engineering background I'm very accustomed
to using numbers that are powers of 2. I therefore couldn't help but
noticing the close relation of such 2 powers to the shutter speeds used on
the OM cameras (and probably other brand cameras too). Look:

2^0 = 1                 -> 1 sec. exposure time
2^-1 = 1/2              -> 1/2 sec. exposure time
2^-2 = 1/4              -> 1/4 sec. exposure time
2^-3 = 1/8              -> 1/8 sec. exposure time
2^-4 = 1/16             -> +/- 1/15 sec. exposure time
2^-5 = 1/32             -> +/- 1/30 sec. exposure time
2^-6 = 1/64             -> +/- 1/60 sec. exposure time
2^-7 = 1/128    -> +/- 1/125 sec. exposure time
2^-8 = 1/256    -> +/- 1/250 sec. exposure time
2^-9 = 1/512    -> +/- 1/500 sec. exposure time
2^-10 = 1/1024  -> +/- 1/1000 sec. exposure time
2^-11 = 1/2048  -> +/- 1/2000 sec. exposure time

It may just be a coincidence (can anyone confirm/deny this?), but these
numbers match up pretty closely. Either way, a thing which by far interests
me more is to speculate a little on how the up-to 4 minute maximum long auto
exposures of the OM-4(T(i)) have been implemented if the above theory is
correct. Suppose 2 powers are indeed used for _all_ shutter speeds, the
range for those long exposures would be extended as follows:

2^1 = 2 sec. exposure time
2^2 = 4 sec. exposure time
2^3 = 8 sec. exposure time
2^4 = 16 sec. exposure time
2^5 = 32 sec. exposure time
2^6 = 64 sec. exposure time
2^7 = 128 sec. exposure time
2^8 = 256 sec. exposure time

Suppose this is true, then the gap between a two minute exposure and a 4
minute exposure would be really big. This leads me to think that a finer
granularity is actually used for the long exposures. However, in case the 2
power range is indeed used, it should be easily verifiable by taking an auto
exposure in a completely dark room, and checking if the camera cuts it off
after exactly 4 minutes (i.e. 240 seconds) or after 256 seconds. Has anyone
ever done this?

For now this is just a little theory of mine (at least regarding the 1/2000
sec. - 1 sec. range; and for the 1 sec. - 4 minute range it's pure
speculation), but maybe someone knows anything about how these shutter speed
timings work and if indeed there is some correlation between the shutter
speeds and the range of 2 powers...

Anyone?

Cheers!
Olafo

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