Measure the voltage. If it is 1.5v+ and the meter agrees with one known
to be correctly calibrated, the camera has been converted. Buy a new
625a (or better yet, get or make from stiff foam an adapter ring and get
a 357 1.5v silver-oxide). Check again with the new battery to be sure.
If the voltage is around 1.35v and the meter is accurate, it hasn't been
converted. You can:
- Try to find a 1.35v 625PX
- Buy an MR-9 adapter, which fits right in the existing battery
compartment, takes a 357 battery and delivers 1.35v to the camera.
- If the camera hasn't been CLAed in human memory, get a CLA. Battery
conversion is usually part of the regular price.
Then you'll be assured of both meter and shutter accuracy and of
reliability.
- Convert it yourself with a diode or battery as discussed voluminously
in the digests and archives.
If neither of the above are true, you have more than a battery problem
and the camera needs professional adjustment.
Digital meters and others with high imput impedance aren't adequate to
assess the condition of batteries for the later OMs, but the drain of
the OM-1(n) meter is low enough that testing the battery voltage without
load should is adequate.
With both mercury and silver-oxide cells, always have a spare. Part of
their superiority for light meters is that they maintain very close to
original voltage ove their entire usefull like, thus assuring accuracy
(or at least consistency). However, this means there is no warning when
they are about to fail, an event that can be quite sudden (Happened to
my OM-1 literally between one shot and the next in Guanajuato, MX).
Alkalines like the 625a slowly lose voltage over their life, subtly
altering meter accuracy long before their relatively obvious slide down
at the end.
Moose
David Bülow-Osborne wrote:
I'm confused about this whole battery thing with the 3 stop error on the
light meter with a 625A battery and the whole thing about converting the
camera for use with that battery type.
How do I know if my OM-1n camera's been converted or not? The battery that's
in the camera right now is a 625A and it seems to work fine, but it's a
really old battery, so who knows if it's putting out it's original
potential.
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