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Yet another extension tube thread

Discussion in 'Lens Lust' started by panda81, Jun 30, 2008.

  1. panda81


    Feb 7, 2008
    Can people give me some advice on which extension tube to buy for a manual focus AIS lens? I don't need the electronic contacts for autofocus, but I would like to have high quality build for the tube between my lens and my camera. Right now, it looks like like the Nikon PK13 is what I want, but I'm not sure if I will lose metering information? I would not prefer the Kenko tubes because a quick search of previous threads said that the tubes are made of plastic, and I don't need the electronic contacts for autofocus.

    Any suggestions or encouragement for the Nikon PK13 appreciated - thanks!
  2. rvink


    Mar 21, 2006
    New Zealand
    The Nikon PK-11A (8mm), PK-12 (14mm), PK-13 (27.5mm) and PN-11 (52.5mm) are all AI compatible and function perfectly with AI and AIS lenses. The best tube depends on the lens you intend to use it with and the magnifications you want. With the lens focused at infinity, the magnification you will get is:
    [tube length] / [focal length]

    For example, the PK-13 is 27.5mm, long, when used with a 55micro you get:
    27.5 / 55 = 1:2

    In plain english, the magnification is proportional to the length of the tube (the longer the tube, the greater the magnification), and inversely proportional to the lens focal length (the longer the lens, the less difference the tube makes).

    Very short tubes like the PK-11A are useful for gaining high magnifications with moderately wide and standard lenses. Ultrawide lenses don't usually perform well - the corners suffer, the working distance is too short and the magnification even with the shortest tube is very high. You can get some interesting effects though. Another use for short tubes is getting a little closer with telephotos while allowing them to still focus a reasonable distance out.

    A medium tube like the Pk-13 is an excellent all-rounder. On standard and telephoto lenses you gain a good boost to magnification, yet the tube is not too big.

    If you want to do high magnification work, the PN-11 is well worth considering. It's big and works very well with telephoto macro lenses like the 105/2.8 micro. It has a very useful built-in tripod mount which has three benefits:
    - it's closer to the center of balance so the setup is more stable and suffers less from vibrations
    - you can rotate from horizontal to vertical format while staying on target for improved compositions
    - overall handling is much improved

    Good luck!
  3. panda81


    Feb 7, 2008
    Thanks for the extensive descriptions! Very helpful.
  4. Toby D

    Toby D

    Mar 7, 2006
    And try and buy them used. There's nothing magic about a new tube vs a used one.
  5. RichNY

    RichNY Guest

    I disagree. I bought a used set on ebay and the air was stale :wink::biggrin:
  6. panda81


    Feb 7, 2008
    Another question, if you don't mind:

    The lens I want to attach the extension tube onto is 50mm, with magnification up to 1:2. With the PN-11, I will probably go beyond 1:1 magnification, right? But will I have the other problems you mentioned in your post regarding poor corner performance and other things, considering that 50mm isn't really a very long FL?

    Thanks again!
  7. Nikkor AIS

    Nikkor AIS

    Jun 5, 2008
    Jerry. Buy every tube Nikon PK tube you can get your hands on. They are just so usefull and work perfectly with everything from 24mm-800mm. As well as Micro Nikkor's like the 55 F4 AIS, 105 f4 AIS, 200 F4 IF AIS. I use them combined with TC 14b, TC301 everyday. IMO "one" of the advantages of the Nikkor AIS line, is the compatabilty with the PK tubes.

  8. rvink


    Mar 21, 2006
    New Zealand
    If you attach the PK-13 to your 50mm lens, magnifications will start just beyond 1:2
    27.5 / 50 = 1:1.8
    Magnifications will go up to about 1:1.4 with the lens focused close so you have quite a small range to work with. That's quite normal with non macro lenses.

    As you say, with the PN-11 you will start slightly over 1:1
    52.5 / 50 = 1:1.05
    With the lens focused close you will get to about 1.2:1.

    50mm is rather a short focal length for this kind of magnification, but the working distance involved is not greatly different from the AFS 60 micro. The 50/1.8 works well over a wide range of magnifications due to the symmetrical optical layout, the increase in aberrations at close range is small. I expect field curvature and other things to creep in, giving less crisp corners, but if you stop down I think you will get good results. If you are photographing 3D subjects like flowers, it is likely the corners will not be in focus anyway so you'll never notice the difference.
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