Will 1.4 volts be close enough?

f/16 · Aug 25, 2015

(I did an APUG search on "675" and nothing came up)I got some 675 zinc air hearing aid batteries for old cameras. I put one in my FT QL and the batt check registered the same as it does with an old mercury battery I have that measures 1.32 volts on the voltmeter. Tomorrow I'll get an o ring to keep the battery centered. Is 1.4 close enough to the 1.3 that many old cameras needed?

Ricardo Miranda · Aug 25, 2015

leicarfcam · Aug 25, 2015

It does work. The Wein cells use the 675 zinc-air battery with a metal spacer ring. The problem is the short 3-4 months lifespan of zinc-air so you will need to carry plenty when out shooting..

StephenT · Aug 25, 2015

Yes, it will work. Personally, I quit using them and just carry a light meter. That probably wouldn't work well for street photography or moving objects, however! The zinc air's will keep quite a while with the adhesive tab intact. Once you pull it, the countdown starts.

f/16 · Aug 25, 2015

StephenT said:
That probably wouldn't work well for street photography or moving objects, however!

Why not?

RalphLambrecht · Aug 25, 2015

f/16 said:
Why not?

a street scene is more a subject for a reflective meterbecause you don't have to be in the scene to meter it as you do with an incident meter in the studio

John Koehrer · Aug 25, 2015

RalphLambrecht said:
a street scene is more a subject for a reflective meterbecause you don't have to be in the scene to meter it as you do with an incident meter in the studio

It's a TTL camera, therefore reflective.

klownshed · Aug 26, 2015

f/16 said:
Is 1.4 close enough to the 1.3 that many old cameras needed?

There are so many variables with old cameras, that the actual voltage isn't too important. The shutter speeds were likely to be quite a way off what the label said even when new.

The important factor with Zinc Air batteries is that they have a similar discharge pattern to the old Mercury batteries in that they stay pretty stable then die unlike SR or LR batteries. It's more important that the voltage is stable than what it actually is. You can then compensate as necessary.

Xmas · Aug 26, 2015

f/16 said:
(I did an APUG search on "675" and nothing came up)I got some 675 zinc air hearing aid batteries for old cameras. I put one in my FT QL and the batt check registered the same as it does with an old mercury battery I have that measures 1.32 volts on the voltmeter. Tomorrow I'll get an o ring to keep the battery centered. Is 1.4 close enough to the 1.3 that many old cameras needed?

The answer is both no and yes.

Normally a camera has a high current draw and pulls down the zero current voltage to the service voltage close to 1.3.

Some meters have low current drain and will read high even on battery test eg the lunasix.

The hearing aid cells can last up to six months but can also leak and still be servicable.

They are fuel cells and breath or leak through their vent holes.

I remove at end of day and replace at begin.

Given they are cheap and readily available in pharmacies they are practical.

Don't lose the o ring - remember Gollum

Edit:

Some meters are ok with any battery voltage, eg K1000 have a differential galvanometer and merely need adequate current capacity.

But most others need 1.33 volts they are only accurate at one light level if they don't get 1.33 volts, the error is dependent on voltage and light level so as a LA voltage falls in service you get a different set of errors at any light level.

A silver cell will need a diode in series or both trimming resistors replaced. The diode adapters are ok if you don't drop one in a storm drain slot. Again they should be selected on current draw.

Dr Croubie · Aug 26, 2015

I'm reminded of a saying I heard in my first job out of Uni: "tune on minimum smoke".

leicarfcam · Aug 26, 2015

klownshed said:
There are so many variables with old cameras, that the actual voltage isn't too important. The shutter speeds were likely to be quite a way off what the label said even when new.

Even with new cameras it was impossible to calibrate each shutter speed to it's specific speed. As a result groups of speeds were adjusted to a tolerance such as setting 1 second brings speeds through 1/15th into tolerance 1/500th brings in speeds through 1/30th and finally 1/1000th. So all speeds were in fact well within tolerance..

klownshed said:
The important factor with Zinc Air batteries is that they have a similar discharge pattern to the old Mercury batteries in that they stay pretty stable then die unlike SR or LR batteries. It's more important that the voltage is stable than what it actually is. You can then compensate as necessary.

While it is true to an extent zinc-air has a similar discharge to mercury, at the end the voltage drops off at a slightly slower rate. If I'm not mistaken SR and LR batteries are alkaline which are poor substitutes since they start losing voltage as soon as a current draw is placed on them. The best solution is to modify the circuit to use silver oxide http://www.colynsfotografs.com/srt.html and http://www.colynsfotografs.com/weston.html which has an identical voltage curve as the original mercury. I've done several cameras and hand held meters this way and I get consistently accurate readings throughout the entire scale. I recently converted a Nikon F using 2 diodes since it uses 2 batteries and my readings have been spot on...

Actually preferred voltage is 1.33-1.37v so yes voltage is very important within its specified goal and you should not have to compensate..

Xmas · Aug 26, 2015

I thought a SR44 was silver oxide.

klownshed · Aug 26, 2015

Yup. SR is silver oxide.

klownshed · Aug 26, 2015

leicarfcam said:
Actually preferred voltage is 1.33-1.37v so yes voltage is very important within its specified goal

The difference between a zinc air battery and original mercury battery is close enough not to make much difference.

The point I was trying to make is just relax. It'll be fine and close enough for Rock and Roll. Of the factors that affect the exposure, a small difference in voltage between the average Mercury cell and average Zinc Air (For they all have a tolerance) is, relative to all the other variables, nothing to worry about.

leicarfcam said:
and you should not have to compensate..

A touch of compensation isn't a big deal. Utmost precision and accuracy, especially with 40+ year old cameras, is not something you'll ever find. And besides, personal preference also needs to be taken into consideration. Which is why some photographers love to shoot Tri-X at, say 320 instead of 400. It's all about getting the result you want.

Close enough is good enough for me. Perhaps that makes me a crap photographer ;-)

f/16 · Aug 26, 2015

I got some O rings today. Looks like O rings and 675 batteries will be good for me. I know they only last a few months, but at 50 cents each, it's not a big expense.

Xmas · Aug 26, 2015

Don't forget they can and will leak and remove them and pop in ziplock bag.

flavio81 · Aug 27, 2015

Xmas said:
Don't forget they can and will leak and remove them and pop in ziplock bag.

How long can they (zinc-air 675 cells) be left without danger of leakage? Months?

leicarfcam · Aug 27, 2015

klownshed said:
Yup. SR is silver oxide.

Any time I come across an off brand battery I don't even bother to test it. It goes straight to the trash so I am unfamiliar with their designations. I only deal with Duracell or Energizer batteries for my cameras..

leicarfcam · Aug 27, 2015

klownshed said:
The difference between a zinc air battery and original mercury battery is close enough not to make much difference.

I agree...

klownshed said:
The point I was trying to make is just relax. It'll be fine and close enough for Rock and Roll. Of the factors that affect the exposure, a small difference in voltage between the average Mercury cell and average Zinc Air (For they all have a tolerance) is, relative to all the other variables, nothing to worry about.

I never said the difference was too great. What I said was the lifespan of zinc-air is the issue... Both types operate within the specified parameters so you should read my responses for what I am saying and not what you assume..

klownshed said:
A touch of compensation isn't a big deal.

It is when you are operating on a strict time schedule...

klownshed said:
Utmost precision and accuracy, especially with 40+ year old cameras, is not something you'll ever find.

Not each and every shutter speed but you can have them all within manufacturer's specifications. I have several Leicas from the late 20's through early 60's and all speeds test within manufacturer's specifications. My Nikon S2, SP, F, and F2 the same..

klownshed said:
And besides, personal preference also needs to be taken into consideration. Which is why some photographers love to shoot Tri-X at, say 320 instead of 400. It's all about getting the result you want.

Print films (B&W and color) have such a wide latitude that even 2 or more stops off is still acceptable but transparency films which I shoot a lot of can and usually do fail at even a 1/2 off exposure so exposure accuracy should be considered very important... If a meter is off it should be taken in for cleaning and calibration..

leicarfcam · Aug 27, 2015

flavio81 said:
How long can they (zinc-air 675 cells) be left without danger of leakage? Months?

I've seen a few that were left in the camera long after they died and no leakage whatsoever was detected. I've never seen a zinc-air leak. I suspect the reason why is because the water created by the process of mixing the chemicals will evaporate.

You may see a couple of tiny droplets around the anode of a zinc-air battery near the end of its life cycle but it is water which will evaporate in a day or two.

Xmas · Aug 27, 2015

Water is not normally a bright green deposit.
Any battery can leak when it's seal fails.
Zinc cells are more properly fuel cells and are not sealed, they do transpire and end of duty is normally dry out.
My two were premium brand.

f/16 · Aug 27, 2015

These zinc air batteries are registering 1.34 volts with the seal still on. Is that normal?

klownshed · Aug 28, 2015

leicarfcam said:
It is when you are operating on a strict time schedule....

...Print films (B&W and color) have such a wide latitude that even 2 or more stops off is still acceptable but transparency films which I shoot a lot of can and usually do fail at even a 1/2 off exposure so exposure accuracy should be considered very important... If a meter is off it should be taken in for cleaning and calibration.

All meters read a little differently. There are differences in how they average a scene, how much weight is given to the centre, etc. And that's without taking battery voltage into consideration.

If you find your meter underexposes a bit for a certain film at box speed, compensate on the ISO dial when you load the film. Easy. Fast. No big deal, it's been done since meters first appeared. A strict time schedule has nothing to do with compensating for your meter, surely? I think we may be talking at cross purposes! ;-)

zanxion72 · Aug 28, 2015

1.34V is not a big difference to 1.40V, but it is to 1.45 that most 1.4V really are. The brighter the light and the more underexposure you will get.

Xmas · Aug 28, 2015

f/16 said:
These zinc air batteries are registering 1.34 volts with the seal still on. Is that normal?

Yes I think so. They are operating on air before sealing, they take a while to get to open circuit voltage with seal removed ~1.4. And some current draw to get back to ~1.3.

They are indistinguishable from mercury in my OM1(n)s. I've still got Mercury cells. With a OM1 if you switch on when you pull the camera from gbag or leave it on in gbag they will be very similar to a real Mercury.

They have a lot more capacity than a Mercury.

But useless in a Lunasix no current draw.

You need to test the camera or meter bright and dark as it is the linearity of the meter that suffers if the battery voltage is not pulled down. My OM1s match the OM4 dark indoors to what passes as daylight here. But if a CdS cell is kaput that won't be good.

Will 1.4 volts be close enough?

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