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Effect of adjusting aperture via adapter

Discussion in 'Adapted Lenses' started by timinsingapore, Feb 23, 2015.

  1. timinsingapore

    timinsingapore Mu-43 Rookie

    16
    Oct 17, 2014
    Most 50mm lenses from the film era (actually most lenses of any focal length) have to be stopped down somewhat to achieve their sharpest performance. I have an adapter with three different positions for aperture control. Open, somewhere in the middle, and stopped down. I bought this for use with relatively modern lenses that do not have their own aperture ring, but were designed originally to be adjusted via the camera. Does 'stopping down' the aperture via the adaptor have an effect on the lens sharpness performance similar to stopping down using the aperture blades within the lens itself? Is it optically the same in effect (leaving aside the difficulty of working out what f/stops the adapter settings are equivalent to, which is a different issue)?
     
  2. HarryS

    HarryS Mu-43 Top Veteran

    919
    Jun 23, 2012
    Midwest, USA
    What kind of lenses? Nikon and Pentax have lenses with no aperture ring, but they have mechanical levers and there are adapters that will move them properly, So stopping them down is the same process, except you don't know where the middle position really is. No effect on optical quality. I've used my Pentax DA lenses like this.

    Canon EOS needs an electrical connection to set aperture. Some M43 users have a Canon DSLR body, so they can set any aperture with DOF preview, remove the lens under power, and then adapt it to M43 that way. Otherwise, they can use an adapter with a second diaphragm. I hear that approach can vignette and otherwise affect quality. Don't know, but it sounds right.
     
  3. timinsingapore

    timinsingapore Mu-43 Rookie

    16
    Oct 17, 2014
    Pentax. The adaptor has its own set of aperture blades which close as you operate the slider. So that is how you adjust the aperture with, e.g., the DA21, which has no aperture ring.
     
  4. HarryS

    HarryS Mu-43 Top Veteran

    919
    Jun 23, 2012
    Midwest, USA
    Wow, I've never seen a Pentax DA-M43 adapter with its own aperture blades. Mine uses a rotating ring to grab the aperture lever on the back of the DA lenses. That way, the lens works as intended.
    closed. adapter. open.
    I will say this particular adapter is hard to find these days. I did find a few for sale on ebay, but none on the amazon, rainbowimaging, fotodiox or bhphoto websites.
     
  5. timinsingapore

    timinsingapore Mu-43 Rookie

    16
    Oct 17, 2014
    I think that is preferable, not least because the aperture adjustment on mine is very crude. I think I will get a simpler adapter that makes no effort to change aperture, and stick to my old manual (Pentax M, and a couple of K) lenses, which are very nice to use anyway.
     
  6. HarryS

    HarryS Mu-43 Top Veteran

    919
    Jun 23, 2012
    Midwest, USA
    Their 19 limited is a great lens, but so is the Panasonic 20mm which will autofocus. . I did not enjoy using my Pentax DA mount lenses on M43, although I only have the consumer zooms 18-55, 50-200 and 16-45. The manual focus ring on those lenses feels like turning a child's toy. Well, they are mostly made of plastic. There's probably plastic gears turning the screw drive focus motor.