Random OM-1 find: battery question

[theolj]

I recently came into possession of an old OM-1N that belonged to a friend's dad who passed away. I compared the meter readings between it and my Canon Elan II, and they were dead similar. I opened the battery compartment to find a Varta V625U battery in it, which I read is 1.5V Alkaline, while the 1N originally took a 1.35V mercury cell. Could it be possible that the camera was modified in some way, or that the battery in it is almost dead? I'm confused as to what batteries I should put in it when they need replacing and when I should do it, as there is no battery check. If anyone has any advice, I would greatly appreciate it. Thanks!

 

[mtnbkr]

IIRC, the OM-1 has a bridge circuit. I know I used standard 1.5v batteries in my OM-1 (not the later N model) for years with no issues.

Chris

 

[Brad Deputy]

It is a common modification to the OM-1 series to modify the circuit to allow 1.5v batteries. Zuiko.com does it. If you find a white sticker from zuiko.com in the film compartment, that would be a dead giveaway.

 

[Larryc001]

I have gone through this week setting up two OM-1 cameras with batteries. There is plenty of information on the internet. My cameras have 625 cells in them that still worked. So I left them in there. Then I cross-checked the om-1 reading with my old handheld meter and my F4 I found the Olympus to be 1 to 2 stops off, so I set my ISO accordingly.

However I will eventually need replacements. The OM-1 does not have a bridge circuit. Since the 625 is no longer available, I referred to this chart:

Camera Batteries - a complete chart - Photoethnography.com's Classic Camera DB

This page has a detailed explanation:

http://buhla.de/Foto/batt-adapt-US.pdf

There are a few that will fit, but only the Wein cell won’t require calibration with an accurate camera or meter.

 

[wiltw]

Through personal testing of the OM-1 meter circuit using PX625 (mercury oxide) vs. PX625A (alkaline) decades ago., when I still had mercury oxide batteries
The OM-1 accuracy of the meter is dependent BOTH on

• actual Voltage output of the battery (which is perpetually declining from 1.5V alkaline)
• actual brightness of the illuminated area being metered

IOW, with the same Alkaline battery in the camera, the amount of meter error was DIFFERENT with a bright scene (e.g. outdoors) vs. a relatively darker scene (e.g. indoors). So one cannot simplistically dial in a constant offset (e.g use ISO 200 meter setting with ISO 400 film). I verified the differences in meter error by comparing OM-1 readings to a handheld meter, pointing the OM-1 at a gray card for its readings.

One can

1. have their OM-1 modified to take 1.5V Alkaline cells, or
2. use 1.4V Wein air cells (which deplete themselvs continuously once activated, even when the camera is not in use), or
3. use adaptors such as the MR-9 which do voltage conversion using 1.55V silver oxide cells.
   (Beware...some so-called 'MR-9' adapters do NOT do any voltage conversion, but require that you use air cells for proper voltage, and which are merely 'physical size adapters' to permit use of smaller diameter air cells in lieu of larger diameter mercury oxide PX625!)

 

[MattKing]

And one can also use physical adapters that allow use of the same battery technology as Wein cells - 1.4V zinc air hearing aid batteries, at a much lower cost.
The hearing aid batteries give short life, but the cost for a dozen is extremely attractive.