Using a Sony LR44 in my Olympus Pen FT?

LambentTyto · Dec 15, 2018

I read you need some kind of adapter to get the FT to work with a newer battery, but I threw this LR44 in here on a whim and the light meter seems to be working. I took the battery out immediately just in case the camera is allergic to it. But if it's not, does this battery work for this camera? Will I get correct exposures?

Not sure if anyone else has tried this or not.

Les Sarile · Dec 15, 2018

It's possible your FT has a diode installed to drop the voltage as mine had the modification. If not I understand the marginally higher voltage would throw the meter off. Of course you would have to compare to a known good meter to determine the accuracy.

LambentTyto · Dec 15, 2018

Les Sarile said:
It's possible your FT has a diode installed to drop the voltage as mine had the modification. If not I understand the marginally higher voltage would throw the meter off. Of course you would have to compare to a known good meter to determine the accuracy.

That's interesting. Well seeing as how I don't have another Pen FT on hand with a working light meter, I guess I can throw a roll in here and see what comes out. I did compare it with the fully manual digital point and shoot I have, but I don't think that's an accurate way to gauge, seeing as how they have different lenses. Any way to check if this diode thing is in there?

Les Sarile · Dec 15, 2018

It doesn't have to be another FT to check the meter, just any other camera meter that is known to be good. Of course you have to match the exposure settings on both cameras in order to match the meter while pointing at an evenly lighted target that covers the full display.

The original meter is factory adjusted to meter properly with a mercury battery at 1.35V while the newer batteries are 1.5V. As I understand it, a germanium diode is installed in series with the battery and it will drop the battey voltage by .3V and then the meter is adjusted to the new voltage of 1.2V. I had the diode mod done when I sent mine in for CLA and was told the mod was easily reversible.

John Koehrer · Dec 15, 2018

If I recall correctly the Pen uses a PX13/PX625 battery. If you just want a physical spacer, I think a #9 O-ring
give s a good fit.

RE meter: A lot of older meters used a balanced bridge circuit that was very tolerant of voltage.
As I understand, it's simply equalizing voltage from two inputs. I said as I understand. maybe someone
will chime in with a circuit or verify that it is a bridge circuit.

Dan Fromm · Dec 15, 2018

When in doubt, Mr. Shining Barn Owl, RTFM. You can download it from: https://www.butkus.org/chinon/olympus/olympus_pen_ft/olympus_pen_ft.htm

I've read the manual. Your camera needs a Mercury cell. These are no longer available. Mercury cells' voltages are very stable. Cameras whose metering systems use them rely on this characteristic, in general -- there may be exceptions -- don't have voltage stabilization circuits. Your camera's meter will be inaccurate if you use an alkaline cell such as the LR44 and the error will change as the cell runs down.

There are several solutions: MR-9 adapter with SR-43, PX-675 size Wein Cell, or PX-675 hearing aid battery. For details and sizes, see: http://www.galerie-photo.com/horseman-4x5-exposure-meter.html

LambentTyto · Dec 17, 2018

A lot of useful answers here. I appreciate it, guys.

CMoore · Dec 17, 2018

Les Sarile said:
The original meter is factory adjusted to meter properly with a mercury battery at 1.35V while the newer batteries are 1.5V. As I understand it, a germanium diode is installed in series with the battery and it will drop the battey voltage by .3V and then the meter is adjusted to the new voltage of 1.2V. I had the diode mod done when I sent mine in for CLA and was told the mod was easily reversible.

I am not following the point of doing that.
If they are going to calibrate the meter to a new voltage, why don't they just adjust the meter to work at 1.5 Volts.?

Les Sarile · Dec 17, 2018

CMoore said:
I am not following the point of doing that.
If they are going to calibrate the meter to a new voltage, why don't they just adjust the meter to work at 1.5 Volts.?

Since I don't have a schematic that was my casual observation too. I am guessing the adjustable calibration range can only be reached with the lower voltage.

MattKing · Dec 17, 2018

CMoore said:
I am not following the point of doing that.
If they are going to calibrate the meter to a new voltage, why don't they just adjust the meter to work at 1.5 Volts.?

In most cases, the meter's circuitry is designed to be linear when the power source supplies a particular voltage.
If you change the voltage, the response (which incorporates the display built into the meter) becomes non-linear, and will only give accurate results at some light levels, not all light levels within the meter's range.
So you can't make the meter work properly with a simple adjustment.
Instead, you make the battery work properly, by incorporating a modification.

Buzz-01 · Dec 18, 2018

For Android phones, there's an app called "Light Meter". Works like a charm for me. There's a similar app for Iphones but I don't recall the exact name.

Have you considered using a hearing aid battery instead of an alkaline cell?
That would not require you to modify the camera and zinc-air batteries would give you fairly accurate metering until the cell is completely empty.
I have read that Alkalines drop their voltage a lot sooner, resulting in a lower voltage near the end of the battery's life.
Not sure if that voltage drop would be compensated when the camera is modified for Alkalines though.

You should be able to use a 675 zinc air battery and a rubber O-ring without any modification to your camera.
I use them in my OM-1 without modification to the camera (just an O-ring around the cell) and metering is spot-on, when compared to the Android app and to my digital SLR.
These hearing aid batteries are dirt cheap (EUR 2,- for 6 cells in my country) and last for a couple of months after removing the plastic tab.
When the plastic tab is still in place, you can store them for a couple of years.

LambentTyto · Dec 18, 2018

Buzz-01 said:
These hearing aid batteries are dirt cheap (EUR 2,- for 6 cells in my country) and last for a couple of months after removing the plastic tab.
When the plastic tab is still in place, you can store them for a couple of years.

Do you order those online or just go to your local drug store?

Wallendo · Dec 18, 2018

Many cameras work well with the 357 battery and no modification. Although not as voltage-stable as mercury batteries, silver oxide batteries show more stability than alkaline.
In my experience the Nikkormat and Olympus 35RC work well with a silver oxide battery without modification, even for E-6 film.
I have 2 Minolta SRT-201's. One has been modified for 1.5V during a CLA, and with the other, I set the ISO down a stop and get good results (I set the ISO to 200 for 400 speed film).
I also have used the voltage modifying adapters which work well, although my SRT-201 demonstrated bizarre behavior when I tried to use one in it. The shutter had issues which resolved when I removed the adapter. The camera itself is mostly mechanical so it makes little sense, but I postulate that a magnetic field was somehow created which caused havoc with the magnets used in the shutter mechanism.
I have read multiple threads like this and at times think that people over-think the battery situation. These old cameras generally do not have sophisticated modern metering systems to begin with, and many users will tweak the ISO settings to adjust over time. The results with alternative batteries are generally within the latitude of modern B&W and C-41 films. Any situation requiring precise exposure is generally beyond the metering capabilities of these cameras to begin with.

Buzz-01 · Dec 18, 2018

LambentTyto said:
Do you order those online or just go to your local drug store?

I normally get them at my local drugstore, but I could also order them online. Shipping usually makes it expensive in that case so I try to combine with something else if I order them online.
One 6-pack of Rayovac 675 cells lasts for about 1.5 to 2 years in my case but I don't shoot that much film compared to others.

And I agree with the poster above me, there is more than enough exposure latitude in modern film, so you shouldn't be too worried...

CMoore · Dec 18, 2018

MattKing said:
In most cases, the meter's circuitry is designed to be linear when the power source supplies a particular voltage.
If you change the voltage, the response (which incorporates the display built into the meter) becomes non-linear, and will only give accurate results at some light levels, not all light levels within the meter's range.
So you can't make the meter work properly with a simple adjustment.
Instead, you make the battery work properly, by incorporating a modification.

Wow...OK.
Are most 35mm SLR meters of that era, like that.?
I was wondering how much difference 200 mV could make. But if i understand you correctly, at some points, it makes A Lot of difference due to the circuit design being "Non-Linear" as you say.
Electronics.....i have just enough knowledge to be dangerous. Cannot believe how often my assumptions have been wrong.
I REALLY envy guys that can look at a schematic and grasp all that it tells.

Using a Sony LR44 in my Olympus Pen FT?

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