So, there was a deal the other day to buy a 1.2 35mm lens or something like that, however the manufacturer of the lens was Pentax. Now they use a K mount and my nikon d3300 uses a F mount.

Does buying an adapter/mount affect the DoF? I have heard that when zoomed to infinity everything becomes blurred and at the lowest too. Meaning you have to play within a short range.

  • So, did you actually buy the lens? "a 1.2 35mm lens or something like that" indicates that if you did, you're not even sure what you bought? Do yourself a favour and don't buy lenses based on "a deal", but do some research first with regard to your needs and lens/camera compatibility.
    – osullic
    Jun 9 '17 at 19:09
  • "...and at the lowest too." At the lowest what?
    – osullic
    Jun 9 '17 at 19:12
  • no I didn't buy it. Like hell was I paying $50 for a $25 lens
    – schnipdip
    Jun 9 '17 at 19:14
  • lowest focal length
    – schnipdip
    Jun 9 '17 at 19:16
  • @osullic Ha no. But hit the wrong link obviously
    – mattdm
    Jun 9 '17 at 21:58

It primarily depends on the flange distance. See this wikipedia article on lens mounts. You'll see that Nikon's F mount is further out than PK's. Meaning that to make this work, you'd have to remove the mount from your Nikon camera, maybe even file some of its frame away, so that the Pentax lens could be placed at the proper distance for infinite to be in focus. Of course, that's hardly ever an option. Using an simple adapter for mounting the PK lens on the Nikon mount would probably add a few more mm, making that lens only work with close objects if you want to get them info focus.

There are adapters with correcting lenses, however, and they may work for this case. But they have their own limitations. They add more surfaces, thereby degrading image quality, and may be in the way of the lens tubus that sometimes reaches into the camera. And their diameter may not be large enough for a wide open lens like the one you wanted to use.

In all, this is a hopeless attempt. On the other hand, with a Sony alpha 7 model, you'd be in a better place - as those are mirror-less, despite being full-frame, their flange range is much shorter, allowing for adapters for many classic SLR lens mounts. But even those will have limit: Usually, those lens only function with manual aperture presets and may also not support open-aperture measuring due to both electrical and mechanical differences.

  • 1
    A fixed mirror? In a mirrorless camera?
    – osullic
    Jun 9 '17 at 21:30
  • The αXX models (e.g. α35, α77, α99) have fixed pellicle mirrors and use the Sony A-mount. The αX models (e.g. α7) and αXXXX (e.g. α6300) are mirrorless and use the Sony E-mount. The αXXX models use the Sony A-mount but also have a reflex mirror.
    – Michael C
    Jun 9 '17 at 23:16
  • Ah, right. I keep confusing the various (non-)mirror systems Sony uses. Thanks for clarifying, Michael - I've updated my answer. I meant the E-mount models. Jun 10 '17 at 8:53

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