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  1. #1

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    normal prime for Pentax 645N with best possible bokeh, native or adapted

    Hello everybody,

    Since I bought my Pentax 645N during spring this year, I have been using my F100 less and less as the Pentax took over my hole field of nature photography, leaving the F100 for light travel and carry around.

    One thing I am missing tough is pretty bokeh. For most of my shots I use the Pentax FA 75mm f/2.8 as I am a big admirer of the normal perspective. While my Nikon AF-S 50mm f/1.4 is not a perfect lens in terms of bokeh, the Pentax leaves a lot to be desired in comparison. For instance, take the image in the attachment. Shot two weeks ago, using the Pentax 75mm set to f/2.8, wide open. I wouldn't call this smooth and I really wish it could be improved.

    Is their a prime lens in the range of 70-90mm that offers a significant improvement in bokeh and can be adapted to the Pentax 645N?

    Best wishes,
    Christian
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  2. #2

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    I too have a P645N and the 75mm lens. Never shot mine at f2.8 but from what I have read adapting other lenses with the exception of the P67 lenses is either not possible or presents great difficulties.

    Pity

    pentaxuser

  3. #3
    adelorenzo's Avatar
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    Medium format lenses don't normally have large apertures... Something to do with depth of field becoming impossibly thin. That being said, if you have heaps of money try the Zeiss/Hasselblad 110mm f2 and let me know how it looks.

    In terms of lenses that can be adapted there are a lot of them. Try Pentacon Six lenses, Carl Zeiss makes a ton of lenses in that mount. Hasselblad lenses are another option.

  4. #4
    Mustafa Umut Sarac's Avatar
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    You can buy a Pentacon, Kiev camera with great smooth romantic bokeh in price of a new Pentax lens.

  5. #5

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    Thanks for your contributions.

    @pentaxuser: just the contrary, there are multiple possibilities. The following systems I know of can be used on the Pentax 645N: Pentax 67, Exakta 66/Pentacon 6, Kiev 80/88 and Hasselblad.

    These should also be possible as they use a flange focal distance that is greater than that of the Pentax 645 system:

    Mamiya RB67
    Mamiya RZ67
    Rollei SL66
    Hasselblad 1600F clones
    Hasselblad (1000F/1600F)
    Hasselblad (200, 500 and 2000 series)
    Rollei SLX

    @adelorenzo: it is not the amount of blur but its quality I am worried about. Technically speaking, the amount of blur is proportional to the crop factor of the format, which means the Pentax 75/2,8 produces equivalent bokeh to an 50/1,7 on 35mm using the same perspective. There is not much lost compared to the 50/1.4 I use on 35mm.

    @Mustafa: I've tested and used the following Pentacon 6 / Kiev 80 / Kiev 88 Lenses on my Pentax 645N via adaptors:

    Mir-26 45mm f/3.5
    Kaleinar-3 150mm f/2.8
    Jupiter-36 250mm f/3.5
    Telear-5 250mm f/5.6 MC
    Tair-33 300mm f/4.5

    I additionally tested them on an Nikon D5100 using live view, every lens throughout every aperture. The Kaleinar had a nice bokeh for a portrait lens, but contrast and sharpness of every lens left a lot to desire. This was visible in scans of 120 film even with resolution as low as 1200dpi. It might be, that the 80mm focal length lenses of the Pentacon Six system are better performer, and that might very well be the case for the Schneider Kreuznach lenses. But at least the russian made lenses did not convince me personally.

    Best wishes,
    Christian

  6. #6

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    You clearly have a very extensive knowledge. Given your extensive knowledge of lenses and fittings what did you think was the gap in your knowledge that others might have been able to cover? I would have been surprised if anyone had been able to add to what we now know to be your extensive knowledge.

    Of course a discussion about others' experience of non Pentax lenses on Pentax cameras might be a worthwhile thread but this wasn't the impression I had. It seemed you had a problem with the bokeh of F2.8 in one Pentax lens and needed help as a newcomer to the P645N.

    Clearly not the case. In fact if we need help we can come to you.

    I hope there is a lens out there that will meet your requirements but don't hold your breath as they say

    pentaxuser

  7. #7

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    Thanks for the kind words, but I think you overestimate my knowledge. Yes, indeed, I know several systems that are or should, in theory, be adaptable to the Pentax 645N. And yes, by coincidence, I've tested several lenses from the pentacon six system to a degree that I am confident, that they are not the kind of lenses I am looking for. But honestly, this is about where it ends.

    I phrased the question in an open manner because I wanted to get feedback especially from users of other systems about positive experiences with prime lenses in terms of bokeh performance. My replies were not indented to show off but to give the posters an informative answer about why I do not indent to pursuit their suggestions. If I have choosen the wrong words, I apologize. Please consider the fact, that english is not my native language.

    Best wishes,
    Christian

  8. #8
    adelorenzo's Avatar
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    If you already have the Pentacon Six adapter I would imagine you would have better results from the Carl Zeiss 80mm or Joseph Schneider 80mm compared to any of the Russian lenses.

  9. #9

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    Well your picture is somewhat of a torture test for lenses, especially older ones. The ultra-creamy bokeh is a more recent phenomenon, and I haven't seen much in the medium format range that performs like (for example) the new Sigma 50/1.4 or 85/1.4.

    You can look up the Pentax 67 105/2.4 lens to see if that is acceptable given your focal length requirement. (I personally love the rendering of that lens.) Another lens which will likely produce smoother bokeh than the 75/2.8 is the Pentax 120/4 macro, again outside your focal length. I have both the 75/2.8 and 120/4 and quite frankly carry around the 45/2.8 and 120/4 almost exclusively.

    Below is a photo with the Pentax 67 90mm f/2.8 LS lens (on a P67ii camera) which I doubt would be starkly different than the 75/2.8 but you can decide for yourself.
    Click image for larger version. 

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    I have other 645N samples which you can browse if you want to: http://blog.seancarpenter.us/tag/pentax-645n/ I have the 45/2.8, 75/2.8, and 120/4 macro lenses for the 645; and the 55/4, 90/2.8 LS, and 135/4 macro in 6x7 format.

  10. #10

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    Again outside of your specifications but if you feel the bokeh of the 75 is unacceptable there is always the 55-110 zoom. However I have no idea if this has a better bokeh. These are just thoughts

    I do not want to direct you away from this forum which in terms of range of knowledge probably is better than any other but as your question is quite specialised you might want to ask it on pentaxforums which specialises in things Pentax and even has a section for P645 and P67

    pentaxuser

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