Reliable and consistent metering with Olympus OM and the likes

[Ivo Stunga]

Just wanted to clear some things up about getting consistent and accurate metering with cameras and light meters that have no built-in voltage regulators and relied solely on the stable (now banned) MR9 mercury battery output.

There are 2 problems sporting such cameras and light meters with today's MR9 equivalents:
1) different voltage: 1.55 instead of required 1.35V - this will give inaccurate readings. To correct it, one must install voltage dropping PCB or use MR-9 adapter.
2) for stable voltage alkaline won't cut it - its output isn't stable over its lifetime and range of temperatures and lighting intensity - silver oxide batteries must therefore be used, they are stable.

For people that want it neat and tidy I recommend going the MR-9 adapter (with integrated voltage drop feature) route that mimics the shape of the banned MR9 battery, fitting nicely in battery compartment. Pair it with silver oxide cell and you're golden!
I use this for about 10 years with OM-1 and OM-1n, and have no problems: exposures accurate for slides, battery lasts many years. And the end of battery is signaled clearly: sudden inaccurate readings. Replace the cheap silver cell and roll on for many more years. And silver batteries usually don't leak - another bonus!

Another route is to:
- install said voltage dropping circuit. Downsides: 1) opening the camera required and soldering involved; 2) you must fit different form-factor silver oxide battery in the battery compartment which can get ugly and unreliable fast;
- use hearing aid batteries - I'd avoid this although their output is stable and close to the MR9. Because of a simple downside: they last for a limited number of weeks draining themselves regardless if you use your camera or not. Creating perfectly avoidable waste in the process. And the battery compartment shape problem persists.


//Post made because even camera technicians tend not to be aware of this - especially of output stability of alkaline Vs silver oxide batteries.

 

[kl122002]

Silver oxide batteries are slightly expensive than alkaline, but definitely won't harm the camera since it won't leak .

The only flaw is about it's availability. Silver oxide batteries are uncommon in my place. I have to order it from internet stores.

 

[Ivo Stunga]

I have to order it from internet stores.

Which isn't a problem, considering the lifetime of the battery - just order a pair and forget about this for 5-10 years.

 

[kl122002]

Which isn't a problem, considering the lifetime of the battery - just order a pair and forget about this for 5-10 years.

Yea, that's what exactly I am doing .

For every time I fix the camera I would use this MR-9 adapter for calibration. I know plenty technician use PX625A and adjust the meter (variable resistor mainly ) but I felt rather insecure to do this .

 

[Ivo Stunga]

I too just popped the readily available alkaline cell of the respective shape inside my camera, thinking that this does the trick. But my exposures were all over the place - so over time I learned all this, bought the respective MR-9 voltage dropping adapter + silver oxide button and am a happy shooter now, exposures on point.
A single silver oxide battery outlasted my camera bag...

 

[kl122002]

I too just popped the readily available alkaline cell of the respective shape inside my camera, thinking that this does the trick. But my exposures were all over the place - so over time I learned all this, bought the respective MR-9 voltage dropping adapter + silver oxide button and am a happy shooter now, exposures on point.
A single silver oxide battery outlasted my camera bag...

Same here, have been asked to clean the batter compartment because previous user forgot the cell inside.

It is not just MR-9, but also MR-44, V27PX and MR-50. They all made by Japanese Kanto Camera .

 

[benjiboy]

I have 2 MR 9 adaptors, one for each of my Canon F 1n's I have used them for year's and have had no problems with them.

 

[runswithsizzers]

//Post made because even camera technicians tend not to be aware of this - especially of output stability of alkaline Vs silver oxide batteries.

Some camera technicians may not know, others may know, but have a different idea about what works.

I had my Konica Autoreflex T4 serviced by a well known Konica technician (now retired). He adjusted my camera meter to read correctly with modern 1.5V batteries. The T4 battery chamber is sized to take two PX625 mercury cells, so I was hoping to use silver oxide batteries of that same size. However, 625 size batteries are no longer available in silver oxide chemistry.

When I asked the Konica technician about what batteries to use, he told me:

"...The voltage drop on alkaline batteries is not that much of a problems if you can’t find them in your area. The alkaline will work but they will not last as long. Example: is a silver lasts 18 months you can expect the alkaline ones will last about 8 to 12 months. But starting voltage is the same on both kinds. The T-4 uses so little voltage, so unless your keeping the camera on all the time the silvers are not needed for the extra expense."​

Rather than using alkaline batteries in the 625 size, my solution is to use silver oxide batteries (357/SR44) in dumb adapters to make them fit.

 

[Ivo Stunga]

The T-4 uses so little voltage, so unless your keeping the camera on all the time the silvers are not needed for the extra expense

My wasted rolls of E-6 film due to exposure reading errors disagree.

Let's take this alkaline battery discharge graph as an example

And compare it to this silver oxide battery graph



At very low draw silver oxide batteries provide ridiculously stable power that drops abruptly. But alkalines go downhill in unison except a couple snowflakes out there in AA form and even these: the jump from full to 1/3 and half is a roller coaster. With old cameras and meters with no voltage regulators your metering will be all over the place.


By now it should be obvious why my exposures were shit with alkalines and consistently great with "expensive" silver oxide batteries. The thing is - the latitude of negative films will mask these reading errors quite well, but with slides a stop and even half a stop difference can make or break a shot.

Note that I'm not an engineer or even "photographer" - just a technically inclined person that shoots slides and loves to project them for that amazement. And was interested why my exposures are far from consistent - some on point, some way underexposed, some way overexposed - all using the average meter in my OM-1 and OM-1n. And the problem "magically" disappearing with said adapter and silver oxide batteries.

 

[kl122002]

Maybe its about the circuit design, which makes some camera drain batteries faster ? My Canon old F-1 (mechanical model) can last very long with my alkaline or silver oxide batteries, but my Pentax Spotmatic F doesn't (I am sure I have closed lens and the camera was in protective case , there is no light enter to trigger the meter.)

 

[Ivo Stunga]

Could be, but the respective chemistry behavior remains unchanged and is a huge factor for accuracy of old equipment.

The more you know

 

[runswithsizzers]

@Ivo Stunga you will get no argument from me! I prefer to use silver oxide batteries as long as they are available as an option.

 

[FriedLouisStudio]

BTW re Silver batteries:

My son is in R&D at Duracell, and he's told me that today's SR44 Silver batteries are essentially LR44 Alkalines with AS LITTLE SILVER AS THEY CAN INCLUDE TO LEGALLY CALL THEM SILVER BATTERIES. They still hold their charge stable for longer than Alkalines... but perhaps not as long as they used to. He says it's true of the other manufacturers too (part of his job is testing other brands for comparison) - competition is fierce and profit margins are slim in battery world.

Just sayin'...

 

[Ivo Stunga]

Observation will tell the story. My exposures are stable with silver buttons and they don't leak, so I can't agree.

 

[kl122002]

BTW re Silver batteries:

My son is in R&D at Duracell, and he's told me that today's SR44 Silver batteries are essentially LR44 Alkalines with AS LITTLE SILVER AS THEY CAN INCLUDE TO LEGALLY CALL THEM SILVER BATTERIES. They still hold their charge stable for longer than Alkalines... but perhaps not as long as they used to. He says it's true of the other manufacturers too (part of his job is testing other brands for comparison) - competition is fierce and profit margins are slim in battery world.

Just sayin'...

Well, I am not surprised to hear that, since by profit making from alkaline seems much better than silver oxide.

Just, since theory is a theory while the reality is the another, would it be a nice if someone would randomly get different batteries and have a discharging experiment on it? Maybe we will find out something surprise us?

 

[Bill Burk]

This is what the meters were designed for: A scientifically reliable 1.35 volts.

I am enjoying voltage regulators

 

[Ivo Stunga]

Next level adapter would be voltage dropping + regulating

 

[Bill Burk]

Next level adapter would be voltage dropping + regulating

Such a thing exists and that’s what makes me so excited. But I only have two of each remaining (1.35v and 2.7v) and that feels like when you’re almost out of your favorite paper.

 

[ic-racer]

Darned positive ground on the OM-1 !

 

[Ivo Stunga]

Such a thing exists and that’s what makes me so excited. But I only have two of each remaining (1.35v and 2.7v) and that feels like when you’re almost out of your favorite paper.
View attachment 364757

Now to shrink this to battery adapter size so no disassembly and battery fitting involved, and I'd pay some money for that.

 

[Anon Ymous]

Now to shrink this to battery adapter size so no disassembly and battery fitting involved, and I'd pay some money for that.

PCBs like this need some extra modification. If you feed it directly by the battery, quiescent current will slowly drain it, so you need to put it after the on-off switch.

 

[Ivo Stunga]

Right. So if/when silver cells won't provide stable output any more, I'll install this PCB

 

[Bill Burk]

PCBs like this need some extra modification. If you feed it directly by the battery, quiescent current will slowly drain it, so you need to put it after the on-off switch.

Right, I had a devil of a time putting in an additional switch for a Gossen Luna Pro. I mechanically linked it to the arm that releases the needle lock, because there’s three different power switches on that gray meter… but all three activate the arm. It’s very nice having the battery check hit the red zone and stay there through the life of the batteries.