Use of 2x converter with various lenses.

Discussion in 'Medium Format' started by stephen_ratzlaff, Feb 24, 2001.

  1. I'm getting pretty close to picking up my 67II system. I have a few more questions regarding the 2x converter.

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    Basically the system I'll be getting is as follows and I need to know if the 200mm lense with its closer focus can be maintained with the 2x coverter in place. I really wanted the 300mm until I saw that the closest focus was around 16 ft.

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    Pentax 67II body
    AE Pentaprism
    105mm lens (I like the fast aperture and the compact design)
    55-100mm zoom lens
    165mm leaf-shutter lens
    200mm lens <OR> 300mm lens [non ED(IF)]
    Auto-Extension tube set

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    NOTE - 300mm ED(IF) I don't have any pricing for, but it's probably out of my price range. If anyone has pricing info, let me know.

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    Now here are the questions:

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    1.) How good is the 2x converter, image and build wise.

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    2.) Can the 2x converter be used with all of the lenses mentioned above, especially the 55-100 zoom, and what kind of performance can I expect on the lenses mentioned above? What kind of performance on the 55-100 zoom? What kind of performance with the 165mm LS lens? etc, etc.

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    3.) Can the auto-extension set be used in conjunction with the 2x converter to give twice the working distance in macro mode? I ask this specifically for the 105mm and 165mm LS lenses as they'd probably be the only lenses I'd use the auto-extension tube set with.

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    On to another non-lens related question. I know that NPC makes a conversion for a polaroid back for the 67II. But has anyone ever tried to order a plain back from Pentax and mate this to one of Polaroid's 545i sheet film backs? I suspect with some modifications and some specific machine shop work something could be made for less than the $700-800 that NPC charges. Fiber optic cable bundles are really not all that expensive anymore, but I was thinking something a bit easier, like a custon mount for the Polaroid back to the Pentax back without the fiber optics. The only hard part would be getting the film in the correct plane of focus, but since it's a Polaroid used to check composition and maybe exposure, I don't think this would be too critical of an issue, a bit fuzzy wouldn't bother me, since the Polaroids aren't really as good a chromes anyhow. Any ideas?

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    Regards

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    S Ratzlaff
     
  2. Wow, that didn't format correctly.

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    The equipment should read as follows:

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    Pentax 67II body;

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    AE Pentaprism finder:

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    105mm lens;

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    55-100mm zoom lens;

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    165mm leaf-shutter lens;

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    200mm or 300mm non-ED(IF) lens;

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    Sorry for the formatting issue.
     
  3. I cannot answer all your question but I can provide some information:

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    Pentax does not recommed using the 2x converter with the 55-100mm zoom
    or the 165mm LS lens. A combination of extension tubes and converter
    should be possible in principle but I have some doubts about the
    resulting image quality.

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    The new 300mm ED lens has an improved close focus distance (2m) and
    sells for 1600 USD at Cayman Camera according to earlier information
    in this forum. However, due to its non-conventional design (IF), 2m
    sounds better than it is in terms of magnification. The lens reaches
    only 1:5.6.

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    From the set of lenses you mentioned I would chose the 200mm lens
    in combination with an achromatic close up lens for close up work (up
    to 1:2, say; not for extreme magnification). My experience with a
    similar combination (2.8/165mm + Pentax T132) at 1:4 is very good.

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    Regarding a NPC substitute I have no idea.
     
  4. The 300 EDIF can be had from Cayman Camera for around $1670. Some of
    your questions about the 2x converter and lens performance can be
    found in other parts of this forum. The 165 LS is a good choice
    because of its f/32 DOF and its Ernostar design(same as the 200
    Pentax). But, to buy the 165 and 200 you might find them to be too
    similar in magnification. The use of converters is a mixed bag. For a
    converter to have optimum performance, it should only be designed for
    one lens(ie the 1.4x on the 800ED). Trying to push converters to other
    focal lengths compromises performance. IMHO I feel the use of a 2x
    on any zoom is mistake mostly because of contrast issues due to the
    total number of elements(17+) involved but also because zooms by
    nature will have sweet spots and weak area of performance. These weak
    areas will be aggravated by the converter.
    Using a 2x converter to increase your macro standoff distance is
    questionable because you could easily use a higher magnification
    lens instead. The 200 works well in macro situations. SR
     

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