There are a number of issues here.
First, the OM-1 and OM-1n were designed to use 1.35 volt mercury
batteries, which are now by and large unavailable and have been for many
years. (The nice thing about mercury batteries was that they last for
many, many years while providing an incredibly stable voltage output --
just what you want in a meter. I've seen mercury batteries that have
lasted a decade or more before going dead!) If you _were_ able to find
a mercury battery for your OM-1, it is probably quite old to begin
with. But while we often hear tales of new "mercury" batteries being
sold here and there, they almost always turn out to be 1.5 volt alkaline
batteries.
In other words, if you recently purchased a "replacement" battery, it's
likely a 1.5 volt alkaline substitute (Type 625A or 625U). The result,
unless your camera has been modified to function properly with the
higher voltage, is that the meter readings will be significantly off.
This error is not linear -- meaning that there is no way to compensate
for the error by, for example, adjusting the ASA.
Or you may have purchased a 1.4 volt "zinc air", or hearing-aid-style
battery, packaged as a replacement for the mercury battery. This is the
kind of battery that's activated when you "peel the seal". These are a
good temporary substitute, but they'll die in a matter of months while
they fade gradually (not a good thing, see below). This will occur
whether you turn the camera off or not.
Next, as noted, it is possible to "convert" your camera so that the
meter reads accurately with 1.5 volt batteries. I'm not certain about
other methods (there are several), but the way we do it you can use
either the alkaline type 625A or 625U batteries or any 1.5 volt type 76
silver oxide battery as well -- it's smaller than the battery chamber,
but I've never seen a case where there was a connection problem.
One of the problems with alkaline batteries is that the voltage "fades"
gradually over it's life -- not a good thing when you're using it to run
a camera meter! So even if you're using an alkaline battery in a
converted OM-1 or OM-1n, we suggest the battery be replaced every year
or so. Maybe that's excessive, but unless you want to carry a voltmeter
around in your camera bag....
Silver oxide batteries are much better -- in normal use, they should
last several years, though not nearly as long as mercury batteries used
to.
Finally, the nice thing about the OM-1 and OM-1n is that in a dark
place, battery drain even while the meter is "on" is quite low. By
"dark place", I mean in a case, or with a lens cap on indoors, etc.
Like this, the battery should last a good long while -- a year or so
with an alkaline battery, longer with a silver oxide, much, much longer
if you somehow found a truly fresh mercury battery. Still, it's a good
idea to turn the meter off when you put your camera away for the day.
But I wouldn't loose sleep over it even if you forgot to!
Oh, yes -- one last alternative to either the zinc-air cell or
conversion process is the MR-9 adapter, which fits inside the battery
chamber of the OM-1 or OM-1n with a silver oxide battery inside. It
reduces the battery output for proper operation. So if your camera is
otherwise in good working order, this may be the best alternative to
keep shooting with the least investment.
96madison@xxxxxxxxxxx wrote:
>
> Hello,
>
> I have an OM-1n with a battery that was replaced last year. I find that when
> I'm
> shooting I'm very conscious about conserving the battery... the result is
> that I'm
> always flipping the meter on and off-- and sometimes this costs me valuable
> time
> (I'm into wildlife photography these days). My question is, does anyone
> have any
> estimates of battery life on these things? Is it necessary to do this, or
> can I just turn
> the thing on for a few hours and leave it that way?
>
> Thanks,
> Rich
> 96madison@xxxxxxxxxxx
>
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