Nikon extension tube with teleconverter

Discussion in 'Nikon' started by C J Campbell, Sep 28, 2007.

  1. C J Campbell

    C J Campbell Guest

    Nikon's AF-S TC series of teleconverters can only be used with a small
    number of lenses because the teleconverters are designed in such a way
    that the rear element of most lenses will contact the front element of
    the teleconverter, possibly breaking them. You can only use the
    teleconverters with lenses that have deeply recessed rear elements,
    such as the 70-200mm AF-S VR.

    Suppose, though, you put an extension tube between the teleconverter
    and the lens, so that the lens elements cannot contact each other. What
    would be the effect on picture quality and exposure?
     
    C J Campbell, Sep 28, 2007
    #1
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  2. You will change the characteristics of the lens and no longer be able to
    focus to infinity. Perfect for macro.






    Rita
     
    Rita Ä Berkowitz, Sep 28, 2007
    #2
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  3. C J Campbell

    Robert Brace Guest

    Don't forget the issue of the "extra mount tab" on the TC's which prevent
    mounting a "normal" Nikkor (not AF-S) until the smaller "extra tab" is
    ground off the mount.
    Beyond that, using a extension tube with the TC should have the same effect
    as using the extension tube by itself on the lens (closer focus, loose
    infinity focus, etc) without the extra magnification of the TC and its own
    exposure & IQ effects.
    With Nikon extension tubes, you would also loose any electrical continuity
    with the lens, such as autofocus with an AF-S lens (which the AF-S TC
    maintain.
    Bob
     
    Robert Brace, Sep 28, 2007
    #3
  4. C J Campbell

    Paul Furman Guest

    Those AF-S teleconverters are optimized for longer focal lengths so it
    may not work well for shorter lenses. I believe the way extension tubes
    effect exposure is that they increase the focal length so the aperture
    becomes smaller relative to the focal length and the f/stop becomes a
    larger number. a 50mm f/1.8 has an aperture diameter of 50/1.8=27.7mm
    and if you add 50mm of extension it's a 100mm lens with an f/stop of
    100/27.7= f/3.6

    Also, you may have to grind off a metal tab on the teleconverter because
    they are designed not to mount to some things. That modification has no
    effect on performance. I did this in order to be able to stack my 1.4 &
    2x teleconverters.
     
    Paul Furman, Sep 28, 2007
    #4
  5. C J Campbell

    Paul Furman Guest

    Oh, and I'm unable to mount my ancient pre-Ai E2 14mm extension tube to
    the front of my AF-S teleconverters, only to the back. It starts
    mounting but won't tighten & snap all the way. This may not be true for
    newer tubes. I can do it but it's not secure and obviously there is no
    aperture or AF connection (but this tube doesn't have that anyways).
     
    Paul Furman, Sep 28, 2007
    #5
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