Lens Shutter Speeds

Discussion in 'Talk About Large Format Gear' started by Keith Haithwaite, Sep 19, 2016.

  1. Keith Haithwaite

    Keith Haithwaite Active Member

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    Out of curiosity I decided to check the shutter speeds on my two large format lenses, a Rodenstock 210mm and a Schneider 150mm and as a control I also checked my MF 45mm f2.8 Pentax lens which has an electronic shutter. The results are interesting.
     

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  2. Stephen Batey

    Stephen Batey Well-Known Member

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    As a matter of curiosity, what is being measured? Is it the total time from start of opening to complete closure, or time fully open?

    Shutter speeds with between lenses shutters are not absolute in exposure terms, as the exposure at a smaller aperture will be greater than that wide open (meaning greater than you'd expect) due to shutter efficiency.

    Interesting reading though.
     
  3. Keith Haithwaite

    Keith Haithwaite Active Member

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    Thank you for your comment Stephen.

    The measurements are for the time the shutter is fully open to the time it is fully closed. As you know, these old leaf shutters operate via a series of gear trains and springs and like any mechanical devices are subject to variances in their speed of operation so, if memory serves, for photographic purposes the standard has always been fully open to fully closed – the only two absolutes in any leaf shutter operation. And yes, you are correct, there is a difference in exposure between a small aperture and a large aperture however it is proportional across the aperture and it is too small to be of any significant importance for our kind of photography.

    Photography as we know it is not a precise science and although it can be interesting to delve into the why’s and where fore’s such as this and for practical purposes in our real world it doesn’t really matter. ;)
     
  4. Graham Patterson

    Graham Patterson Member

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    Acceptable tolerances for mechanical shutters are surprisingly large. Flutot's quote between 30% and 20% plus or minus the marked speed http://www.flutotscamerarepair.com/Shutterspeed.htm. Consistency is more important. If I can get my exposure right to within 1/3 of a stop I am happy, and I cannot reliably set an aperture to 1/3rd stop. So I don't mind a slightly fast or slow shutter if it is consistent.

    Between my poor brain, the equipment variability, and the vagaries of natural light, getting to within a half stop of what I intended is good going :cool:
     
  5. Keith Haithwaite

    Keith Haithwaite Active Member

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    .. and that's just the start of it!:)
     
    Last edited: Sep 20, 2016

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