12-40 aperture blades supposed to close when turning off camera?

Discussion in 'Native Lenses' started by fadingphoenix, Dec 28, 2013.

  1. fadingphoenix

    fadingphoenix Mu-43 Regular

    Dec 27, 2013
    This is just an oddity I observed a while back when trying to look through my dismounted 12-40. Unlike other lenses I've owned which keep the aperture blades wide open the 12-40 seems to close them when the camera is turned off. I haven't seen anyone else comment on it, so maybe it's a more common occurrence among lenses than I realize. It's something I've been curious about though. Has anyone else noticed this? Is there a reason for it? Is my lens behaving oddly?
  2. JeanLucX

    JeanLucX Mu-43 Regular

    Oct 3, 2013
    mine is closed. I notice a few lens of mine with f2.8 have closed aperture blades so maybe it is common among lenses with f2.8 aperture.
  3. fadingphoenix

    fadingphoenix Mu-43 Regular

    Dec 27, 2013
    Interesting. I'm a recent convert from the old 4/3rds and I've never seen that behavior before.
  4. Rudy

    Rudy Mu-43 Top Veteran

    Jan 24, 2013
    Oakland, CA
    Makes it less likely that you would burn a hole into your sensor should the camera be laying around pointing at the sun.
    Old Leica rangefinders with cloth focal plane shutters had a similar problem...

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  5. zulfur666

    zulfur666 Mu-43 Veteran

    Jan 30, 2014
    my 12-40 has a very tiny opening I assume it would be f22 but its not completely closed. I still see light through it. Where my 60mm 2/2.8 Macro is wide open.
  6. dolbydunn

    dolbydunn Mu-43 Regular

    Dec 28, 2013
    As a former camera repairman I have seen the Leica C with the cloth shutter having small 1/16" holes burned thru the shutter curtains by the focused rays of the sun. I had forgotten about that until you mentioned it. Cool.
  7. mattia

    mattia Mu-43 Hall of Famer

    May 3, 2012
    The Netherlands
    Both Sony FE primes do this to. Very obviously visible.