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Thread: A query on focal lengths

  1. #1
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    Default A query on focal lengths

    Hi all,
    recently acquired a CZ jena biometar 80mm in pentacon 6 mount...it came with a p6 to m42 adaptor and i top this off with a m42 to k-mount adaptor..

    the p6 to m42 adaptor is about 3-4cm "tall" and putting it onto the biometar extends its length..it reminds me of a extender tube now...

    since its 80mm....multiplying by 1.5 makes it 120mm after crop...

    i was wondering..would this p6 to m42 adaptor actually make my biometar longer in focal length?


    i dun have a longer lens or a superzoom to confirm the lens focal length so i was wondering if any of you guys ever used a pentacon 6 mount camera with a p6 to m42 on a APS-C DSLR..
    The Few...The PROUD...

  2. #2
    Senior Member giantcanopy's Avatar
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    Default Re: A query on focal lengths

    Quote Originally Posted by ardnirun View Post
    Hi all,
    recently acquired a CZ jena biometar 80mm in pentacon 6 mount...it came with a p6 to m42 adaptor and i top this off with a m42 to k-mount adaptor..

    the p6 to m42 adaptor is about 3-4cm "tall" and putting it onto the biometar extends its length..it reminds me of a extender tube now...

    since its 80mm....multiplying by 1.5 makes it 120mm after crop...

    i was wondering..would this p6 to m42 adaptor actually make my biometar longer in focal length?


    i dun have a longer lens or a superzoom to confirm the lens focal length so i was wondering if any of you guys ever used a pentacon 6 mount camera with a p6 to m42 on a APS-C DSLR..
    no. the 120mm will still remain 120mm. the adapter/s only served to make sure ur lens focuses to infinity on the dslr. If u look at it in another way, the pentacon bodies have longer flange-focal distance to achieve infinity focusing. u will need to "add some thickness" to do the same on ur DSLR ( which has a shorter flange focal distance i assume ) .

    ( but of course while using on an APS-C , the crop factor applies, the lens focal length does not change )

    ryan

  3. #3
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    Default Re: A query on focal lengths

    Quote Originally Posted by giantcanopy View Post
    no. the 120mm will still remain 120mm. the adapter/s only served to make sure ur lens focuses to infinity on the dslr. If u look at it in another way, the pentacon bodies have longer flange-focal distance to achieve infinity focusing. u will need to "add some thickness" to do the same on ur DSLR ( which has a shorter flange focal distance i assume ) .

    ( but of course while using on an APS-C , the crop factor applies, the lens focal length does not change )

    ryan
    ahh
    okok...thanks....
    The Few...The PROUD...

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