Compensating for modern batteries in my SLR?

FishyFish

FishyFish

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My Olympus OM-1 has a 1.5v alkaline battery powering the light meter. As the original battery was a 1.35v mercury cell, the new battery gives an off-reading on the light meter (from my tests it appears to under-expose in comparison with my digital camera or light meter apps).

Other than buying a custom battery, a convertor, a retro-fit, or just winging it and taking shots when the meter's needle says they will be overexposed by a certain ammount, is there a formula for compensating for the discrepancy? My quick tests seem to indicate a difference of about 2 stops (a test gave 1/8sec exposure at f/2.8 on my digital camera at ISO 125, but the OM-1 was showing 1/30sec with the same settings). Does this sound about right?

I'm wondering if, for example, rating 400ASA film down to 100ASA on the camera speed-dial will be a quick fix to compensate for the battery?

Your advice is welcomed oh wise ones of Talk Film & Conventional. :)
 
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The wein cells don't seem to last long. A few months by all accounts. I've been looking into exactly the same issue as I have the Minolta that takes the 1.35v batteries. Also the vivitar takes them. The adaptor thingies are NLA and stupid money.

I'd think a 1.5v lithium if you can find one of some of the right size with some doobry to drop the voltage to 1.35v that copes with the reduced voltage so still only drops it to 1.35v would be the right type of thing. Or a standard battery that is just 1.4v. The hearing aid batteries are 1.4v but they only last a month once activated but as they're so cheap they probably could be considered something you'd use and change frequently.
 
Had the same issue with my Gossen Lunasix 3 light meter, this takes 2 of the old mercury batteries. Air cells didn't last 12 months and aren't cheap as the meter needed 2 of them. In the end I managed to pick up another meter off eBay that came with a professionally made converter to take 2 x 1.5v (or whatever) silver oxide batteries, dropping the voltage to what's required. I imagine something similar might be available for the OM1? If so, 'first loss is best' might be the right philosophy in the long run if you intend keeping the camera and using it regularly?
 
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The converter thingies were on the smallbattery company site but they're listed as out of stock when I've checked.
 
I'm busy nagging an electronics friend of mine to make me some that would fit more than one camera :)

The dual battery camera models aren't as bad with it as the single battery camera models. I have one of each so I hope to test them. I did notice the meter in the vivitar camera was 'live' all the time the battery was in so that's a great way to flatten the battery. I'd have expected it to only be live when you half pressed the shutter.
 
Mr Badger said:
Had the same issue with my Gossen Lunasix 3 light meter, this takes 2 of the old mercury batteries. Air cells didn't last 12 months and aren't cheap as the meter needed 2 of them. In the end I managed to pick up another meter off eBay that came with a professionally made converter to take 2 x 1.5v (or whatever) silver oxide batteries, dropping the voltage to what's required. I imagine something similar might be available for the OM1? If so, 'first loss is best' might be the right philosophy in the long run if you intend keeping the camera and using it regularly?
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I've just put a roll of FP4 in it this morning (wish it's been some Poundland Agfa now!) and am going to try shooting it with the camera set at ISO 80 and trust the meter. Or I could shoot half at 80 and half at 100 and then compare when I get the negs. Hmmm...decisions, decisions.
 
srichards said:
I'm busy nagging an electronics friend of mine to make me some that would fit more than one camera :)

The dual battery camera models aren't as bad with it as the single battery camera models. I have one of each so I hope to test them. I did notice the meter in the vivitar camera was 'live' all the time the battery was in so that's a great way to flatten the battery. I'd have expected it to only be live when you half pressed the shutter.
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Is the light sensor for the meter fitted around the lens on the Vivitar or is it on the body? A lot of cameras with 'always on' meters have the sensor around the lens so when you fit a lens cap, the meter is essentially off. Alternatively, your only option is to remove the battery if you're not going to use the camera for a while.

With regards to the voltage, the converters basically fit a Schottkey Diode inline between the battery positive lead and the camera. You could take the bottom plate off the OM1 and solder a diode in yourself then use a washer to narrow the battery tray and a spring to fill in the gap if you're going to use an LR44. Alternatively, if you fancy a bit more DIY, page 6 onwards in this document shows you how to make your own adapter using a flat PX625 battey and the kit that is available for 4.50 euros from a dutch supplier.

http://www.butkus.org/chinon/batt-adapt-us.pdf
 
I bought the expensive adapter for my OM1 and it works well but I still regret the expense, as it's so easy to put a Schottky diode in yourself. See http://olympus.dementix.org/Hardware/PDFs/OM1DiodeVer2_1C.pdf

There is so much room to fit the diode inside the OM1. If I ever get another camera which would require the voltage drop, I'd transfer the adapter to it. I bought some 1N5711 Schottky diodes very cheaply on e-bay. If you're competent with a soldering iron, I suggest you try the conversion yourself.
 
stevelmx5 said:
Is the light sensor for the meter fitted around the lens on the Vivitar or is it on the body? A lot of cameras with 'always on' meters have the sensor around the lens so when you fit a lens cap, the meter is essentially off. Alternatively, your only option is to remove the battery if you're not going to use the camera for a while.

With regards to the voltage, the converters basically fit a Schottkey Diode inline between the battery positive lead and the camera. You could take the bottom plate off the OM1 and solder a diode in yourself then use a washer to narrow the battery tray and a spring to fill in the gap if you're going to use an LR44. Alternatively, if you fancy a bit more DIY, page 6 onwards in this document shows you how to make your own adapter using a flat PX625 battey and the kit that is available for 4.50 euros from a dutch supplier.

http://www.butkus.org/chinon/batt-adapt-us.pdf
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I did try this myself Steve and it's damn nearly impossible to cut the slot in the dead PX625 with a junior hacksaw and a needle file. I think if you have access to a machine shop, or maybe own one of those Dremel things, then it might be a bit easier. It's definitely going to be fiddly though and if you're prone to losing your temper, then warn family and neighbours about the impending bad language.
 
Yeah, I didn't say it was a simple DIY ;0) I reckon I'd end up swearing at it too so would rather pay a bit more to have a ready-made adaptor instead!
 
Having read through I think the best solution is to use the hearing aid batteries that are 1.4v and just use them for a week and get rid if you're not going to use them within the next 2. They have the right voltage and right personality and at about £2 for 6 they're cheaper than the alternatives unless you use the camera a lot.

I did buy some alkaline 625s as a direct replacement and wonder whether a bit of tin foil packing would discourage the full 1.5v?
 
stevelmx5 said:
Is the light sensor for the meter fitted around the lens on the Vivitar or is it on the body? A lot of cameras with 'always on' meters have the sensor around the lens so when you fit a lens cap, the meter is essentially off. Alternatively, your only option is to remove the battery if you're not going to use the camera for a while.

With regards to the voltage, the converters basically fit a Schottkey Diode inline between the battery positive lead and the camera. You could take the bottom plate off the OM1 and solder a diode in yourself then use a washer to narrow the battery tray and a spring to fill in the gap if you're going to use an LR44. Alternatively, if you fancy a bit more DIY, page 6 onwards in this document shows you how to make your own adapter using a flat PX625 battey and the kit that is available for 4.50 euros from a dutch supplier.

http://www.butkus.org/chinon/batt-adapt-us.pdf
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Not sure where the meter is to be honest! I have just put it back in its case and put the battery on top to remind me there's no battery in it!

Good find on that pdf. I need to read it properly but it seems to be the definitive article on everything to do with these batteries and solutions.
 
Some of those early cameras were in sime way "balanced" so the voltage was not so critical; Pentax Spotmatics spring to mind...
 
I had the diode put in my OM1 as part of a CLA & run it off an SR44 battery now. They hate alkaline batteries from what I have read. Don't give consistent meter readings. Miles Whitehead / MW Camera Repairs did mine.
 
Around £50 for the CLA including it. This was last year. If your OM1 hasn't had a CLA recently then it might be worth having one done to get the foam seals out from around the prism. They were fitted to most OM1's & rot & ruin the silvering on the prism. You start seeing black marks in the viewfinder.

I have a brass adapter that I got off ebay that takes an SR-44 sized cell up to PX625 dimensions.
 
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I use a 675 zinc/air hearing aid battery and an O ring to locate it - right voltage (well 1.45v) and lasts a few months - £1 for a pack of 4 at Poundland
 
Does he do hi-Matics? If I like it, it might be worth doing. This is why I really like the trip. No batteries :)
 
Unless the camera requires battery power to operate the shutter, which the OM-1 doesn't iirc, I'd simply use a handheld meter and forget the faff of voltage variations etc

Been through all that and found it to be a complete PITA.
 
srichards said:
I'm busy nagging an electronics friend of mine to make me some that would fit more than one camera.
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The easiest thing to do would be to get a schottky diode fitted in series with the cell in each camera. That will drop the voltage by about the right amount and will allow you to use easily obtained 1.5v cells.


Steve.
 
Steve Smith said:
The easiest thing to do would be to get a schottky diode fitted in series with the cell in each camera. That will drop the voltage by about the right amount and will allow you to use easily obtained 1.5v cells.


Steve.
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Whatever the solution it needs to only be active when the camera is active otherwise it will drain the battery away.

I'm not sure whether the hi-matic wants 3v as it has a pair of cells side by side so it might be effectively 2.7v. So I was wondering about using one lithium 3v cell instead of fiddling about with the LR44s. I have found one which seems to be the same height. (CR1/3N or something) I also found another which would probably fit in side ways and leave room for possible gubbins like a voltage regulator thingy doodad. (CR1/2N) It's just finding one that is inert until the camera is active.

The other crude solution I thought of was a bit of marker pen/insulation tape on the light cell cover to reduce the amount of light getting in so it would compensate for the voltage being wonky. If the over voltage means it over exposes then you should be able to reduce the light by some amount to compensate?? I'm not sure how I'd use the LR44 size batteries in the minolta as the 640s are huge. 16mm diameter and 11mm high. The vivitar 35 EF takes one of the smaller size so an LR44 drops right in.
 
srichards said:
Whatever the solution it needs to only be active when the camera is active otherwise it will drain the battery away.
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If it's in series with the cell, current can only flow through it when the meter is active. i.e. exactly the same as when it is not fitted.


Steve.
 
I'm looking into finding a source of ND film to put over the light meter. If I can find some which is is one stop equivalent then you can stack it for a stronger effect I would have thought.
 
srichards said:
I'm looking into finding a source of ND film to put over the light meter. If I can find some which is is one stop equivalent then you can stack it for a stronger effect I would have thought.
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See if you can get Lee Filters to send you a swatch book. It's intended for theatre lighting techs as it has samples of all of their coloured gels in it, but it also has 1, 2 and 4 stop (I think) neutral density filters.


Steve.
 
srichards said:
If the over voltage means it over exposes then you should be able to reduce the light by some amount to compensate?
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Over voltage means it will under expose as the meter thinks there is more light than there actually is. However, your idea of partially blocking or filtering the meter cell will work as that will reduce the amount of light the meter sees, hopefully back to the correct level.


Steve.
 
srichards said:
I'm looking into finding a source of ND film to put over the light meter. If I can find some which is is one stop equivalent then you can stack it for a stronger effect I would have thought.
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If you're just looking to adjust the exposure indicated by the meter by only one stop, why not alter the ISO setting of the loaded film? That would be a lot easier than sticking something over the meter window.
 
NickT said:
If you're just looking to adjust the exposure indicated by the meter by only one stop, why not alter the ISO setting of the loaded film? That would be a lot easier than sticking something over the meter window.
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Because I want the option of doing that as well to give more flexibility about how much incorrect exposure can be handled :)
 
I got a roll of FP4+ back from Peak Imaging today which I'd rated at ISO80 on the OM-1 speed dial and they seem to have mostly come out ok, so my estimate of the meter being about 2 stops out seems to be fairly close to the mark. I'll probably keep using this rough'n'ready method of getting a reasonably correct metering while I decide whether to fork out on a CLA and battery upgrade.
 
I've found more ways for it not to work. 1/2N cells are just a teeeny weeny bit too big to drop into the battery compartment on the hi-matic. Grrrr. So annoying. It would be even better if you could squeeze a single CR2 into the battery compartment as that is a common size.

Stacking 4 SR44s and taping them up is a possible solution if I could work out how to do it and make it 3V and not 6V.

It's so annoying that the alkaline 640 equivalents seem to be unavailable now as well as the zinc air versions in that size.

Waiting for the 1/3n as that should fit vertically but it's not very high capacity unfortunately. No better than a pair of stacked LR44s. In fact a pair of SR44s would be higher capacity. Also wondered whether you could use an automotive mini blade fuse sideways to fill the other side of the battery compartment. I will find a way to do this!
 
Have you tried just stacking 2 SR44s to give you the 1.5v then fill in the gap with a metal washer or just a ball of foil? Not the prettiest of solutions but you won't see it once the cap's on!
 
I have emailed Minolta Dave for ideas and to find out whether the E has the bridge circuit in it. I don't want to fry anything as I know what a clot I can be!

If I could get the alkaline 640As that excell used to do then it would be a lot easier but they seem to be stupid money and in the US only.
 
srichards said:
I have emailed Minolta Dave for ideas and to find out whether the E has the bridge circuit in it. I don't want to fry anything.
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You won't. If it was designed for 1.35v, 1.5v isn't going to harm it.


Steve.
 
stevelmx5 said:
Have you tried just stacking 2 SR44s to give you the 1.5v then fill in the gap with a metal washer or just a ball of foil? Not the prettiest of solutions but you won't see it once the cap's on!
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the ball of foil works.......I had to do it with a stack of lr44 cells in a minox gt 35
 
Minolta Dave does conversions to 1.5v batteries as this camera has pots to correct for the differing voltage in the metering circuit. Much neater solution I think. They use the 625A batteries so I'd think using SR44s wouldn't be a problem in future either if the 625S become tricky to find.

It may as well have a check over too as the cost of that is less annoying than ruining yet another roll of film even if it is only Vista!
 
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