Biasing the ASA to compensate for 1.5v Battery

Discussion in 'Rangefinder Forum' started by rjs003, Jun 6, 2006.

  1. rjs003

    rjs003 Subscriber

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    I have been thinking about this for some time now and wonder if anybody else is doing as I have done. I have a few older rangefinders ie. Konica Auto S2 and Yashicia that orignally used mercury batteries which are no longer available. In the absence of these batteries I'm using 1.5v and 6v batteries and biasing the ASA setting to compensate for the larger voltage. I have read that using the higher voltage batteries will cause the auto function to over expose the film. Has anybody done any scientific research on this matter, or just plain experimented as I have done.
     
  2. PhotoJim

    PhotoJim Member

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    Since your meter readings will vary as the battery ages, you're chasing a moving target. For colour print film you might be able to find a compromise setting that will work alright, but otherwise you'll never get accurate exposures.

    The only exception is that some cameras (eg most Pentax Spotmatics) use a circuit that only wants voltage, and it doesn't care what voltage it gets. In this case, no compensation is necessary.
     
  3. Donald Qualls

    Donald Qualls Member

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    The best alternative, for accurate exposure, for the old mercury batteries is either a zinc-air cell like a hearing aid battery (short life) or Wein cell ($$$); these have almost identical voltage and discharge curve (albeit over shorter lifespan) as the original mercury cells. Next best, and probably most efficient, is silver oxide. Though these cells have too much voltage (1.55 V instead of the 1.35 V the meter usually wants), they have very similar discharge curves, and make offsetting the film speed a usable technique. They cost a good bit more than alkaline, but they also last a lot longer; enough so that, unless you get your alkalines at the dollar store (I get LR44 10/$1), it'll just about pay the difference in cost. And once you find the correct offset for your meter (easily done by comparing against a good meter with the correct battery), it'll be right until the cell dies.
     
  4. Marco Gilardetti

    Marco Gilardetti Member

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    Okay. Now REALLY, HONESTLY, did you notice any kind of difference in your exposures? Really, ANYTHING that makes you think that you need a compensation?
     
  5. rjs003

    rjs003 Subscriber

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    Yes.... especially when using color film. But then again I only use the manufactures ASA guide numbers as just that, a guide. I have found that using my own personal guide numbers produces the best results. By the way I shoot mostly Black and white.

    When shooting EFKE 100 using my view camera, I generally rate it at ASA 50 and get really well exposed negatives. This may be a function of my hand held meter or it may be just the way I shoot.
     
  6. juan

    juan Subscriber

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    I do that for my Nikon F - I use a silver oxide battery. I also have a Nikon FG which takes an alkaline battery. I found a full contrast scene - from Zone II to VIII, put the FG on a tripod with a 50mm lens, and pointed it at the scene. I adjusted the shutter and f/stop to get the meter centered. Then I replaced the FG on the tripod with the F, transferred the lens to the F, and set in the same shutter speed and f/stop. Then I adjusted the ASA setting until I got the meter centered.

    Is this scientific? I don't know, but I now reliably shoot color negative film using the F's internal meter.
    juan
     
  7. tchamber

    tchamber Member

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    If you're willing to spend the money (~$30) you can get an MR-9 adapter that will step down the voltage, so you can use a non-mercury battery. I got one for an OM-1 and it seems to work fine, eliminates the need to offset the ASA speed.
     
  8. Jim Jones

    Jim Jones Subscriber

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    My Yashica TLectro SLR (the version that uses two 1.35 Mallory PX-640 mercury cells) meters accurately over a range of battery voltages like at least some Pentax Spotmatics. However, there is a caveat on Michael Butkus' site Michael Butkus' site about using 1.5 volt batteries in that Yashica in place of the original 1.35 volts.
     
  9. Gerald Koch

    Gerald Koch Member

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    Another alternative, if you are handy with a soldering iron, is to insert a diode in the battery circuit to drop the voltage of a silver oxide battery down to 1.35. An 1N34A germanium diode is used. You can get then for about a quarter. There are instructions on the web.
     
  10. Flotsam

    Flotsam Member

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    I use Silver batteries in my Nikon F and adjusted the film speed to match a known accurate handheld.
    I had heard that voltage changes over the life of the batteries would cause readings to change over time so I checked it fairly frequently figuring that I'd just make further compensations as time went by. It only takes a moment as I'm going out the door and is by far the least expensive way to deal with the problem.

    Funny thing, after about two years, I haven't had to make any further film speed compensations since I did initially when I first put the batteries in. I guess the discharge curve in silver batteries can't be that big a problem.
     
  11. BrianShaw

    BrianShaw Member

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    This is what I did with my grey Luna Pro and Canonet. It works well. But since I don't care for the Canonet I seem to have a rather expensive spare part bouncing around in the bottom of my camera bag just waiting to get lost.
     
  12. Tom Duffy

    Tom Duffy Member

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    when I tried using 1.5 volt batteries in my Leicaflex SL the response was non-linear, i.e., an exposure compensation that worked in bright light was way off in low light and vice versa. I finally bought 10 mercury batteries to tide me over.
     
  13. polaski

    polaski Member

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    Gossen USA equippped my old Luna Pro S with an adapter that allows me to use L44's, and they work fine.
     
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  15. Doug Knutsen

    Doug Knutsen Member

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    As a sucker for any rangefinder camera, particularly ones branded Yashica, Konica, or Canon, (but I'm not really choosy - as long as the camera is a rangefinder) I snap them up whenever I find one at a garbage sale. Batteries for them? No problem, if you're in the U.S.. Just go to "Batteries Plus." They've always had suitable replacements for the old mercury jobs. I checked with the local store (Salem, OR) and they told me they have over 200 stores across the U.S.. Sure beats messing with soldering guns, expensive adapters, etc.

    Doug
     
  16. copake_ham

    copake_ham Inactive

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    A couple of thoughts on this:

    1) If you're shooting slide film the latitude should be plenty wide enough to compensate for the relatively minor difference in readings from a 1.5v vs. 1.35v battery.

    2) Probably okay with most other film too.

    3) Do some side-by-side comparison readings b/w your "overpowered" RF and a more recent camera or outboard light meter and see how far "off" you really are. A slight adjustment in the appropriate direction of your f/stop on the lens may result in a more "accurate" compensation than changing the ISO/ASA setting on the camera.
     
  17. Ryuji

    Ryuji Member

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    When I restore my old Konica Auto S2, Autoreflex T series and other cameras, I usually recalibrate the meter to give accurate reading with silver oxide cells (if the camera is designed for 1.35V) or lithium cells (if 2.7V). In the case of Auto S2, there is a potentiometer on a small PCB on the meter unit, right behind the rangefinder mirror that is linked to the lens cam. It's shown in the fourth picture of this link:

    http://wiki.silvergrain.org/wiki/index.php/Konica_Auto_S2#Light_meter

    Just blow it up and see the pot with green and black wire. One goes to the meter, and the other go to the CdS wire (connected right next to the battery well). The camera is + ground as you see the red wire grounded in the picture.

    I had to restore one of my Auto S2 the other day, and this camera had many small problems evrywhere (I hate that!) I had to take pretty much EVERYTHING apart. So I decided to make photo documentation... though some parts I was too into fixing and didn't get to take much pictures. (well, wait until next time I pick another one up!)

    Anyway, the top link is this:

    http://wiki.silvergrain.org/wiki/index.php/Konica_Auto_S2

    CdS cells have only approximate linearity (conductance roughly proportional to irradiance intensity) and there is need to compensate for this. Also, if the meter indicates the correct aperture, what's displayed is also logarithm of the irradiation intensity. Some sophisticated meters use multiple CdS cells in combination to alleviate this, and a simple meter circuit like Auto S2 compensates for this by varying the spacing for each stop difference. For example, check the space betwen f/4 and f/5.6 (wide), and f/11 and f/16 (narrow). This is due to multiple factors, such as the minimum (residual) resistance of CdS cell, resistance of the meter and the series resistor, as well as the nonlineariy of the CdS cell itself. In lock-needle exposure automation like ones used in Konica cameras, the meter deflection is transferred to aperture driving lever. In this camera, the nonlinear relation between the deflection and f/stop value is mostly compensated at this level. (In cameras for interchangeable lenses, the lever angle and f/stop must be well standardized, and often must be linear, but for fixed lens cameras, they can design just for one lens.)

    So what happens if you use a battery of higher voltage and compensate with the film speed? The problem is that the sensitivity offset is not constant at f/2 end and f/16 end. That's the problem. If you set the offset for one end and the other end may be a stop off. Yes, only a stop. Not a big deal. But I prefer to eliminate this offset error. The offset is greater in the f/16 end, so people who routinely shoot in f/1.8 to 4 range may not notice much.

    Match needle cameras have simpler mechanism and of course their solution is also simpler.
     
    Last edited by a moderator: Aug 1, 2006
  18. naturephoto1

    naturephoto1 Subscriber

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    As with the Rollei 35S cameras, the meter can also be adjusted for the change from the 1.35 V Mercury to 1.5 V Alkaline battery by a repairman. If you are comfortable enough and you have the tools and reference, you could make the adjustment yourself.

    Rich
     
  19. jmailand

    jmailand Member

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    These are 1.4v batterys,#675, made for hearing aids. Thier almost identical in size to lr44's (see scans attachment below) . I bought some, but I haven't tried them yet. Has anybody tried using these. I was going to use them in a konica c35 but the cameras battery holder wants a battery with a smaller negative contact diameter like a wein cell or the original battery. But I think they would work with other cameras that have a battery holder that can use lr44's.

    James,
     

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  20. Ryuji

    Ryuji Member

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    I know this is useless information for most average end users. But I thought to say that it's very often an easy matter to recalibrate meter. No need to have diagrams or service manuals, although they are certainly helpful.

    Most cameras can be recalibrated, and it's easy to follow the circuit to get the metering circuit diagram. (Most, if not all, competent repairmen keep a notebook and pencil handy during work.) Based on this diagram, anyone who has basic knowledge of circuit theory can figure out which pot needs to be turned to which direction. The amount, however, has to be calibrated against known standard...

    The above doesn't apply to electronic shutter cameras, such as Yashica Electro's. I'd hate to work on those cameras. But even those could be worked on...

    Zinc air cells are good in terms of voltage stability... but they don't last long once used. I prefer to use silver oxide or lithium cells (alkaline is inferior in terms of discharge property). Those lithium cells allow me to almost forget that the camera used battery!
     
  21. Woolliscroft

    Woolliscroft Member

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    Using OM cameras with slide film I do find a just noticable underexposure using 1.5v batteries, although it's only very slight. I bias the meter to overexpose by 1/3 of a stop and that gets it pretty much right. With B&W and col neg, the difference falls into the noise, but I still tend to leave the bias on as it does bring up deep shadow detail a bit.

    David.
     
  22. mgb74

    mgb74 Subscriber

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    I've used the adapter described here: http://www.buhla.de/Foto/batt-adapt-US.pdf

    I purchased, rather than build mine. It has worked very well with my Rollei 35 and Canonets with a silver oxide battery. I've also used hearing aid batteries with appropriate spacers in my Spotmatic.
     
  23. PeterB

    PeterB Subscriber

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    Ironically Zinc air cells have the highest capacity [mAh/kg] of ANY commercially available battery technology available today.

    There is one type of zinc air cell being made specifically for photographic equipment to replace mercury cells, but they charge a premium for them because they have no competitors. They are known as Wein cells see http://www.weincell.com/ Don't believe all the marketing hype they sprout on their site (there are errors), but I think the one year shelf life (after peeling off the tab) could be credible.

    I have tried to find out more info from them directly, but until they reply to me I am assuming that they have simply made the air holes smaller. Having smaller air holes means a lower maximum current (not a problem for camera meters), but it also means that they should take longer to (self) discharge as the oxygen can't diffuse through as fast.

    The other disadvantage of zinc air cells them is that the maximum current (i.e. amperage) they will deliver is substantially less than both alkaline and much less than silver oxide (and also mercury cells), but this should not be a problem for the camera meters which draw small currents (much less than the 10 to 15mA limit of zinc air cells)

    regards
    Peter
     
  24. Gerald Koch

    Gerald Koch Member

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    While you may find a battery that is the correct physical size, other cell characteristics may make it unsuitable as a replacement for a mercury battery. Some cameras use a bridge circuit that is tolerant of voltage differences. However some camera circuits may be damaged by higher voltages and amperages than those for which they were designed. The only batteries currently available in the US for camera use are alkaline, silver oxide, zinc-air and the older carbon-zinc types. Only the zinc-air cells are a safe direct replacement for mercury cells. The other choice is to reduce the voltage of a silver oxide cell by using a converter or by modifying the camera circuit.

    Lastly and most importantly, alkaline and carbon-zinc batteries cannot be used because of the steep voltage change during discharge. One of the reasons a mercury cell was originally used in these cameras was because there is only a small voltage change until almost the end of the cell's life. Today only a silver oxide cell has the same characteristics as a mercury cell.
     
  25. Doug Knutsen

    Doug Knutsen Member

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    Gerald: Are you telling me that the alkaline batteries I get from Batteries Plus are potentially harmful to my cameras? I have six different Yashicas from the Electro 35 series, all of which I love, and if I'm liable to damage them with the alkaline batteries I'll switch over to adapters. (I'll also quit telling people to get their battery replacements from Batteries Plus!)

    Doug
     
  26. Gerald Koch

    Gerald Koch Member

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    The Yashica Electro 35's seem to do well with alkaline batteries as their circuit is not that voltage sensitive. I have several myself and they seem to do quit well. What I am referirng to are those cameras that have a match needle meter design and use a button battery like the 675. For such cameras a zinc-air or silver oxide cell is usually required.