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Strictly for the Macro Fan.

Discussion in 'Adapted Lenses' started by Dave in Wales, Mar 3, 2015.

  1. Dave in Wales

    Dave in Wales Mu-43 All-Pro

    Nov 5, 2011
    West Wales
    I have found a source of NOS Canon FD 28mm f2.8 lenses, ideal for reversing onto my EM1

    Reluctant as I am to cite other forums, I came across this......
    http://www.dpreview.com/forums/post/35014905

    I've been messing about with macro and reversing for well over 50 years but I cannot come to terms with what this guy is proposing.....an adaptor between the body and the reversing ring.
    If the adaptor is required, it does nothing other than act as a spacer/stand-off.

    Mind you, his results do look impressive.

    However, I have never reversed a Canon on M4/3 before.

    Your opinion Gentlemen/Macro Nuts is sought.
     
    Last edited: Mar 3, 2015
  2. fredlong

    fredlong Just this guy...

    Apr 18, 2011
    Massachusetts USA
    Fred
    The combination of the geometry of the lens and the short registration distance of m4/3 probably caused the lens to focus beyond infinity. It was just too close to the sensor.

    A lens reversed is still the same focal length. Usually reversing it "adds" extension. A retro focal lens like a 28mm for 24x36mm format will likely have its optical center close to or beyond the back of the lens body. I would expect reversing it without any additional extension would work fine.

    Fred
     
  3. Rudy

    Rudy Mu-43 Veteran

    449
    Jan 24, 2013
    Oakland, CA
    I think the problem he's running into is that the back focal length of the lens is longer when it is reversed. When using just the reversing adapter the lens focus apparently is beyond infinity, so the extension tube is needed to get int in range. Usually one would use reverse mounted lenses on a bellow setup, so this should not be a problem.
    If you look at the lens design of a macro lens that is meant to be used around 1:1 magnification you will find that it is almost symmetrical.
    Lenses that are made for lower magnification will have larger front elements and will be very asymmetrical in design.
    If lets say you had a lens that was optimized for 0.1 magnification then the same lens would also work well for magnifications of 10x when reversed. However everything in between will be no man's land and not be very well corrected with the lens reversed or not.
    Rudy
     
  4. Dave in Wales

    Dave in Wales Mu-43 All-Pro

    Nov 5, 2011
    West Wales
    The critical thing as I see it now is not to get the reversed lens TOO CLOSE to the sensor.
    Further away does not matter, as this 'gap' is often filled with bellows or extension tubes to increase magnification.