Olympus OM-4 Multi Spot Metering

Discussion in '35mm Cameras and Accessories' started by Chan Tran, Mar 9, 2014.

  1. Chan Tran

    Chan Tran Member

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    I wonder how the meter in the OM-4 would calculate the multi point spot metering. I know you can measure up to 8 points. But as an example of say 3 points. You have the camera on aperture priority say f/5.6 and the measurements are 1/1000, 1/125 and 1/30 for example. What shutter speed the OM-4 would pick as the average of the 3?
     
  2. onepuff

    onepuff Member

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    Set my OM-4ti to ISO 100 and tried it. Answer is just over 1/125th of a second (or under if you know what I mean).
     
  3. Chan Tran

    Chan Tran Member

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    Thanks.
    If I give 1/1000 = 10 (10 stops from 1 second)
    1/125=7 and 1/30=5
    Average those would give me 7.3333 so I think the shutter speed would be 1/160 second. A third stop from 1/125. Is that what you got by trying?
     
  4. thuggins

    thuggins Member

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    It averages the multiple readings. You can see this clearly if you watch the meter display as you pick successive points.
     
  5. mopar_guy

    mopar_guy Subscriber

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    The shutter speed is a linear average of the spot metered areas. In Auto mode, it will be calculated by the camera based on TTL meter readings of the spots. In Manual Mode, it works like Match Needle metering where you still have to select Aperture and Shutter speed manually. If you want to bias the reading more towards shadow values, take two or more spot readings of dark areas.
     
  6. onepuff

    onepuff Member

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    Yes. The indicated speed was 1/3 stop faster than 1/125 so the actual speed would be around about there.
     
  7. aoleg

    aoleg Member

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    There is a neat trick allowing you to bias the exposure towards some areas. You can, for example, measure the same spot twice (let's say it's 1/1000), and then add another measuring (let's say 1/250). The average will be calculated as an average of three values: 1/1000, 1/1000 and 1/250.
     
  8. kivis

    kivis Subscriber

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    A feature that never took hold in other cameras. Why? I thought and still do think it is an awesome feature.
     
  9. Xmas

    Xmas Member

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    Two main reasons

    - Not many people use a spot meter, yes zonies do
    - It was slow the button pushes needed to be deliberate

    Most people can use an OM1 more easily.
     
  10. kivis

    kivis Subscriber

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    Ok I will stick with my Nikon's, but still I love the idea.
     
  11. Les Sarile

    Les Sarile Member

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    Probably because you are Nikon bound, you're not aware that both the Canon EOS1V and EOS3 have multispot metering.
     
  12. Ricardo Miranda

    Ricardo Miranda Member

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    So did a few Minoltas via a custom card, actually called Muti-spot.
     
  13. Poisson Du Jour

    Poisson Du Jour Member

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    By mean-weighted averaging of x number of readings with or without highlight and shadow inclusions.

    The stepless shutter in the OM4 means the shutter speed can be higher or lower than the numbers you see and also vary during the exposure (like many stepless shutters). The mathematical 'how-to' is irrelevant and cannot be accurately determined by conjecture.
     
    Last edited by a moderator: Oct 20, 2015
  14. Bill Burk

    Bill Burk Subscriber

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    I don't believe the OM-4 changes exposure time on the fly during exposure once spot mode is in effect.

    But I swear you are right Poisson Du Jour about the time not being what you see on the bars... Last weekend I was out shooting Panatomic-X in dense forest and exposures that seemed metered as 1/8th were taking what felt like 1/2. I'm not 100% sure I was in spot mode, it could have been full auto when I noticed that.

    Times like these are what make me appreciate the OM-1 which, if you choose 1/8th... you get 1/8th.

    Oh right, I could put the switch to manual.
     
  15. Poisson Du Jour

    Poisson Du Jour Member

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    Lock the exposure value to prevent drift. The OM4 is not alone in doing this. I can count the EOS 1, 1N, 1V and EOS 3 as also varying during exposure if the exposure metered has not been locked.
    If you invest in a camera of precision, we should rejoice that the modern things can indeed keep track of subtle differences in the exposure as it happens. One reason I'll never be separated from my trusty EOS 1N! :smile:
     
  16. Bill Burk

    Bill Burk Subscriber

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    There isn't an exposure lock button on the OM-4 "per-se" but as soon as you hit the "Spot" button, you have taken a reading that will be used for the exposure (So "Spot" locks the exposure). There's always manual.
     
  17. Poisson Du Jour

    Poisson Du Jour Member

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    Yes, manual. What is the OP using the camera in?
    I had never heard of a spot meter until I came away with the OM4, and in the four years of owning two I learnt the fundamentals of spot, highlight and shadow control — these fundamentals are still in use today, albeit with a Sekonic spot e.g. up to 9 readings, highlight, shadow, MW-average. Shoot. It was an invaluable camera for examining the "mysterious" (to me then) relationships over a scene's tonal/spectral area and even more invaluable to factor in highlight and shadow detail. Kodachrome 200 (the professional version) probably didn't need such critical differentiation across the scene, but it was still a fun learning experience. If it were not for me being long-finished with ardent use of 35mm, I would probably have bought one. Or two! :smile:
     
  18. Xmas

    Xmas Member

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    You are correct in spot the exposure is not off the film...
    In auto spot you get a step less exposure at the aperture you have currently!
    In manual spot you need to adjust the aperture for 1/3 of a stop.


    All Winbni
    Would it not be nice if...
    As well as slow buttons
     
  19. cuthbert

    cuthbert Member

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    T90 too.
     
  20. blockend

    blockend Member

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    Yes. I never used mine. Easier to evaluate the scene and compensate.
     
  21. Ricardo Miranda

    Ricardo Miranda Member

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    When Asahi Pentax introduced in 1970 the Electro Spotmatic, that was one of the advantages of the Aperture-Priority system highlighted. On the ES and many other Aperture-priority the shutter is stepless, but it is "locked" at time of pressing the shutter button.
    The OM-2 and -4 had a real time shutter adjustment during exposure via OTF.

    I don't believe the Canons you mentioned have an OTF system for ambient light, only for the flash.
    As far as I remember from my own EOS-1N and -3, the Evaluative meter relies in SPD cells housed in the prism, unless I'm very much mistaken.
    And so, they can't be seeing changes in exposure value when the mirror is up and the shutter is open.
    What you might be referring to is the "cybernetic" capability, i.e. the EOS will switch to an appropriate shutter/aperture pair if one chooses a value not available.
     
  22. Xmas

    Xmas Member

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    Think you mean it has both
    a) evaluative multi metering or
    b) off axis spot metering

    As well as other modes

    The OM4 has mean, shadow and highlight 'evaluations' but optimised for E6 (like some other spot meters) rather different.

    Nikons meters are centre biased (ie most are) and you need to push the backlight or hold button when provided and necessary again rather different.

    You need to understand how any of these work in different situations!
     
  23. Les Sarile

    Les Sarile Member

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    No two ways about it as the manual precisely list it as Multi-Spot Metering.
     
  24. wblynch

    wblynch Member

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    I find the ESP metering of the OM-PC much more useful in real life than the multi-spot metering of the OM-4/T/Ti
     
  25. thuggins

    thuggins Member

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    Although a practiced eye can get very good results with an OM-1, the multispot meter on the 4 is invaluable in complex and unusual lighting.