Pentax KM meter sadness

Discussion in '35mm Cameras and Accessories' started by phatcactus, Aug 8, 2005.

  1. phatcactus

    phatcactus Member

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    Hello all. I've been lurking around for quite a while, but've never posted. But now I have a problem. So sad.

    I've just noticed a strange problem with the meter in my new (to me) Pentax KM. It seems to work fine, until you hit a half-second at ASA 400. Then the meter jumps way, way up, and not even blocking the lens will bring it back down. The behavior is proportional throughout the ASA range. At ASA 100, the meter jumps up at B. At 3200, 15.

    So I'm wondering, could it maaaybe just be a problem with the battery? I took the number listed in the manual to Radio Shack, and they gave me its modern-day equivalent. Could it be that? Please? I'd really hate for there to be something more serious wrong with it.

    It's probably not worth getting fixed, as it makes fine exposures otherwise and is pretty predictable. But it's one of those things, ya know?
     
  2. gnashings

    gnashings Inactive

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    I know what you mean - I hate a niggling issue like that - even if it does me no real harm. I know ita there and it annoys me to no end!
    I am not very familiar with your particular camera - but let me ask you this: Where is the at rest position of the needle? Does it jump in that direction? If it does, it will most likely be a battery issue. Unless there is some partivular KM gremlin that I, having never had a Pentax, may not be aware of...
    Here is hoping! Best of luck,

    Peter.
     
  3. Kiron Kid

    Kiron Kid Member

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    Have you given the battery contact points a cleaning with Vinegar? Oftentimes, that will do the trick.

    Kiron Kid
     
  4. BradS

    BradS Subscriber

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    Batteries are cheap and need to be replaced fairly frequently in these cameras. Definitely start there. Then consider....

    The issue might also be related to oxidation in the film speed selector contacts or, even in the shutter speed selector. The proper fix for either of these involves disassembly and cleaning but, a quick fix can sometimes be effected by simply "excercising" the switch contacts. Simply rotate each selector through its full range ten times or so and see if the issue is resolved (get a new battery first though).

    If neither of these does the trick, and you're going to loose sleep over it, have the body serviced by a qualified technician. One can expect to get a Pentax KM completely overhauled for around $125 and can usually expect to pay something like $70 or so to have one cleaned, lubricated and adjusted (consider this regular maintenance).
     
  5. burn1138

    burn1138 Member

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    could be thats the light level where any dimmer and the meter is unreliable. my dad's old chinon does a similar thing, it raises a red flag behind the meter needle.
     
  6. resummerfield

    resummerfield Subscriber

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    I think that may be normal. The Spotmatic was set up to only meter in a specific range. It sounds like you are trying to meter out of that range.
     
  7. phatcactus

    phatcactus Member

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    Very interesting. Thanks for all the suggestions. I'll try a new battery, but the worst that can happen is I'll have to pay closer attention, right? Not so bad. I'm surprised there might be a set range for where the meter works though.
     
  8. BradS

    BradS Subscriber

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    Actually, I think the previous two posters have got it right. The camera is trying to tell you that the set of conditions exceeds the metering range of the built in meter. If this is in fact the case, the point at which the needle goes off scale should also depend upon the aperature set (i.e. f-stop) - alternatively, it may depend upon the maximum aperature of the lens you have mounted.

    Light meters most definitely have limited ranges over which they are capable...most manufacturers specify this range something like this....

    Metering Range: EV 1 to 20 at ISO 100 and with f/1.4 lens

    (i.e., from 1 sec. at f/1.4 to 1/4000 sec. at f/16)

    On the Pentax SP-1000, meter boundaries are indicated by a litte flag in the arrow that points to the selected shutter speed.
     
  9. phatcactus

    phatcactus Member

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    Yeah, I really should check the manual before I freak out. There is indeed a limit to the the KM's meter, although I'm still trying to see if it matches my results. According to the manual, at ASA 100 and any aperture between f/16 and f/1.4 (ie. not f/22), I should be able to meter between 1/4 second and 1/1000 second. But mine works all the way down to a whole second, including f/22.

    I wonder if the numbers on my ASA dial are just shifted all over somehow. The manuals chart for ASA 100 looks a little like my results for ASA 400. But then would my film be underexposed? Agh, I don't know. Like I said, it's not gonna keep me up at night. Just thought I'd ask if anybody'd ever encountered it before.

    Thanks everybody!
     
  10. BradS

    BradS Subscriber

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    That manual says the metering range of the KM is: EV3-- 18 for ASA 100 film.

    1 second at f/22 is EV 9 - well within the meter's range. On the high end, the meter is going to run out of gas (according to this manual) at 1/1000 second at f/16 (which is EV18). I suspect that your camera and meter are perfectly fine.
     
  11. Gerald Koch

    Gerald Koch Member

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    Nikon aperture priority cameras (such as the KM, EM, and others) had the "feature" that the meter would peg and refuse to budge is you chose an aperture outside of the allowable range for a particular film speed. This was poorly documented and often causes confusion.

    When I first purchased a used EM, I thought the meter was behaving erratically and almost sent it in for repair.

    Another feature with some Nikons is that the meter will not turn until two or more frames have been wound off to get past the film leader.
     
  12. Gerald Koch

    Gerald Koch Member

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    The intention of my post was to point out that not only Pentax but also Nikon produced poor documentation. The first sentence got a bit scrambled in that the KM is not a Nikon Model.

    The Pentax ME Super is a little less confusing because it uses LED's rather than a needle.

    Too many cameras with similar model names EM, ME, KM, ...!