Light meters in the dark

Discussion in '35mm Cameras and Accessories' started by hdeyong, Sep 24, 2013.

  1. hdeyong

    hdeyong Member

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    I have a couple of Olympus OM's that I use all the time, and they're always kept in a bag. Just a habit I got into long ago, when I realized I couldn't stand a camera hanging around my neck. Plus, the protection, etc.
    Anyway, sometimes I forget to turn the camera off, (for several days at a time), and it doesn't seem to affect battery life.
    So, my question is, if the light meter has nothing to meter, is there little or no battery drain?
     
  2. Xmas

    Xmas Member

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    confirmed e. g. the Rolli 35T slip case is like a changing bag saves cost of switch

    but Pentax K1000 and earlier spots have a auto
    light sensitive switch to reduce residual to zero in near dark

    no way of telling how good your bag is...

    so undesirable unless bag is light tight and you use caps switch off & affix cap before sticking in bag

    the OM1 sensors can detect light leaking from eye piece

    you need to be using silver or air battery for 1/3 of a stop accuracy.., the Pentaxs can use any battery with some life left, they have a balanced bridge circuit

    OM are nicer though... furtively hides awaiting wrath

    but if you are using om2 leave them off all the time they only need to be on if the shutter is slower than 1/30 they will meter off the film ok in auto when speed faster than 1/30

    The other OMs are automatic but you need to down load the manual.
     
    Last edited by a moderator: Sep 24, 2013
  3. McErland

    McErland Member

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    Both my OM10 and OM2 can stay on for days without any problem! In the end though, you just have to change battery earlier than you would if it would have stayed of.. My OM10 hasn't had a new battery since March 2012, and it still works like a charm after all the times I forgot to turn it of or it accidentally got turned on when carrying it.
     
  4. Xmas

    Xmas Member

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    An OM10 goes into a low battery drain condition after 90 seconds unless it is in a tight fitting g bag, and the first pressure tripped repeatedly, if you carry a OM1 all day with cap off and switched on in good light it uses battery all day.

    You don't need to turn an OM2 on if you know the shutter speed is going to be more than 1/30. It does an OTF and 1st blind pattern exposure reading even when switched off doing an ok exposure from 1/1000 to1/30.

    I never turned my OM2 on or replaced batteries.
    Don't think you need to turn on an OM10 either just hit the shutter for good exposure.
     
  5. Peltigera

    Peltigera Member

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    There is no need to turn on the OM 10 so long as you are happy with the camera selecting the shutter speed. Mostly I am, but if the light is not too good, it might select a shutter speed a tad too slow without you realising it.
     
  6. Xmas

    Xmas Member

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    Thanks for the confirmation.
    but if you leave it off and drop it back in gbag it won't have to worry about how dark it is if there are loose articles in with it tripping the first pressure.
    The OM10 and OM2 real clever.
     
  7. E. von Hoegh

    E. von Hoegh Member

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    The photocells in a meter circuit have very high resistance in the dark, as the light level increases the resistance falls - this is how meters work.
    Depending on the type of cell, the resistance can be on the order of megohms when no light is falling on it.
     
  8. hdeyong

    hdeyong Member

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    That makes sense. Thanks E.
     
  9. Chan Tran

    Chan Tran Member

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    It would be true for cameras like the OM but for modern cameras like a Nikon F5 for example, if the meter doesn't time out and shut itself off it would draw about the same current even with the lens cap closed.
     
  10. Xmas

    Xmas Member

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    true but each of the OMs are different.
    a simple CdS cell draws no current in a changing bag but a off on switch is desirable as they will work (draw current) in overcast moonlight even if the meter or coupling does not register it.
    Only the OM1n and OM1 have a CdS cell.
    The other OMs have photocells which react more quickly for offthe film or shutter curtain metering and spot metering depending on model.
    I normally omit the battery from my OM1s.
    Unnecessary complication, bit like a phone in pocket really.
    Though with an F5 you can show people you have not taken their photo.
    hee hee hee
     
  11. MartinCrabtree

    MartinCrabtree Member

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    Howzat?
     
  12. MattKing

    MattKing Subscriber

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    Show them the back of the camera - "nothing here":D
     
  13. Xmas

    Xmas Member

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    Thought the F5 had a dinky LCD on rear door, though not suitable for chimping, all you need to do is demonstrate it a bit of economy with truth mayhap.

    I get lots of requests for deletion... very few for film.
     
  14. Ralph Javins

    Ralph Javins Member

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    Good morning;

    "Light meters in the dark." Yup. E. von Hoegh has accurately described the basic way that a light sensing cell or element of a light meter works. In fact, one of the standard rated qualities for that cell is called "dark current" or how much current may flow through the light sensing cell in total darkness at a standard specified test voltage. It is inversely related to "dark resistance."

    Back in the early 1960s when the then new Minolta SR-7 came out with its built-in Cadmium-Sulphide (Cd-S) light meter on the front of the camera, the owner's manual recommended storing the SR-7 in the optionally available leather case. While the manual did not specifically say why, one reason was to keep the Cd-S cell covered and dark. The SR-7 developed a reputation as "a battery eater." It seems that many American photographers were just leaving the camera sitting on a shelf or table or something, and the light meter faithfully kept metering the light of room where it was. The next year, in response to the complaints by owner's, Minolta installed a small 2 position rotary switch on the bottom of the SR-7, producing the variant I call the SR-7a. (The later SR-7b had a 3 position rotary switch with the "BC" or Battery Check position.) Then if the owner did not put the camera into the leather case, and left it on the shelf or desk, and also remembered to turn the light meter switch "OFF," nothing happened. The light meter battery lasted for a year or more.

    Well, the owner's manual did suggest storing the camera in the leather case, although not explaining that you were also storing the camera light meter in the dark and saving the PX-13 or PX-625 battery. This was an incident where the ability of the average American photographer to ignore the owner's manual, and to complain about the result, did produce a modification of the camera.
     
    Last edited by a moderator: Sep 28, 2013
  15. elekm

    elekm Member

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    With the Nikon FE, the film advance was the meter switch. When pushed against the body, it locked the shutter release and turned off the meter.

    The Minolta XD 11 didn't have an on-off switch. The LEDs in the meter would go off after a short period. Magazines, at the time, warned photographers to ensure that nothing was resting on top of the camera and pressing the shutter release, which activated the meter. They said it could drain the battery in a short amount of time.

    The Olympus OM-2 does have an on-off switch for the meter.

    The Pentax MX has a shutter release lock, which keeps the meter from being activated accidentally. Same goes for the Rolleiflex SL35 E.
     
    Last edited by a moderator: Sep 28, 2013