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Vintage Legacy, issue 23 April 2016

Discussion in 'AP Magazine Feedback & Suggestions' started by Roy5051, Apr 20, 2016.

  1. Roy5051

    Roy5051 Well-Known Member

    Forgive me, but I am totally confused by statement number two on page 12, which states:-

    "The distance between the lens and the camera sensor (the flange distance) must be equal to, or greater than, the distance between the lens and the camera sensor on the original camera".

    Wikipedia states:-

    "the flange-to-film distance the lens is designed for must be greater than that of the camera body it is to be adapted to, giving room for the adaptor."

    Does this say the same thing? The quote from AP seems to suggest that the flange distance on the new camera must be greater or equal to the flange distance of the camera that the legacy lens was designed for, by stating "the original camera", which I took to mean the camera that the lens was originally designed for. We know that this is incorrect, as you cannot use M42 lenses on Nikon F bodies and get infinity focus for that reason. So, I am assuming that, when Matt Osborne talks of the "original camera" he must be talking about the new camera that you are hoping to fit the lens to, not the original camera that the lens was designed for.

    Can someone confirm this, please?:confused:
  2. El_Sid

    El_Sid Well-Known Member

    Basically if you want to achieve infinity focus with a lens when mounted to a camera it was not designed for the adaptor fitted must ensure that the lens to film/sensor distance, often called the lens register or lens registration, is the same as that specified for the original system the lens was designed for. If it's too far away the lens won't focus to infinity (the effect is the same as adding an extension tube), if too close it may not focus at all or only over a limited range.

    CSC type cameras have very short registrations meaning that pretty much any lens can be fitted if an adapter that maintains the correct registration for the lens is available. With SLR camera it gets trickier. Most have registration distances that are pretty similar which tends to limit the range of lenses that can be fitted, if only because the adapter cannot be made thin enough to allow infinity focus. Canon's EF mount is among the most versatile as it has a much shorter registration distance than most other systems and quite a wide range of adapters are available - ironically because it has the same registration as the older FL & FD lenses the only way to use those is to buy an adapter with additional optical elements to compensate for the adapters thickness.
  3. Roy5051

    Roy5051 Well-Known Member

    Yes, I understand all that, but the write-up in this week's AP seems to confuse the issue. Perhaps a clarification from the AP staff or the article writer would be in order, as new users may very well be totally confused. I think the original wording in the article was erroneous, and could have been much more clearly put.
  4. Ffolrord

    Ffolrord Well-Known Member

    Just buy a Pentax DSLR, get any K mount lens (last 40 years) and put it on your camera. Prior to that M42 screw thread lenses via simple adapter. All this registration and focus to infinity business seems a bit over complicated to me. You get metering, focus confirmation, infinity focus, and the mirror won't slap into the lens. Oh and stabilisation is in the body so the lens doesn't matter. Job done. Why make it difficult?
  5. El_Sid

    El_Sid Well-Known Member

    Having reread your post several times I suspect the confusion arises from the term flange distance. I think if they'd said "The distance between the lens and the camera sensor (the registration distance) must be equal to, or greater than, the registration distance between the lens and the camera sensor on the original camera" it would be clearer. By using the term flange distance they seem to have implied the actual distance from the mount face on the camera to the sensor rather than from the mount face on the lens.
  6. Roy5051

    Roy5051 Well-Known Member

    El Sid

    Sorry, but I still have a problem with that. I think if they had said that the registration distance on the old (film) camera must be equal to or greater than the registration distance on the new (digital) camera that you want the old (film) lens to fit on. I know it is a mouthful, but it would be much clearer than the explanation as printed.


    I agree, Pentax got it right in the first place; as you say, almost any lens produced by Pentax and their Clones over the past 50 years or so will fit on their digital SLRs (except the Ricoh PKA clones (PKA/R), which had an extra button on the lens that could get stuck in certain apertures in a PKA camera mount and jam the lens and camera together.

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