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Thread: Pentax 645 zoom lenses

  1. #1
    Senior Member Ed Hurst's Avatar
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    Pentax 645 zoom lenses

    Hello all,

    I am getting on pretty well with my Pentax 645D, mostly using 6x7 lenses and an adaptor (though I do have a couple of 645 lenses as well). However, one thing that I am finding is that I would like, on occasion, to use the camera more speedily - with zoom and autofocus. I am looking for authoritative advice on the optical quality of the various different zooms. Having invested in the body, I am eager not to throw the advantage away by using an optically substandard lens in the pursuit of speed - that would be illogical! I recognise that there will be some compromise in quality compared to a top class prime, but want the lens to be pretty damn good nonetheless - throughout the zoom range and at all apertures.

    Can anyone provide me with guidance on this please?

    Best wishes,

    Ed

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    Re: Pentax 645 zoom lenses

    Hi Ed,

    I own the 645 80-160 and my example is OK, not great but not bad vs primes. It's certainly not as sharp as my 120 macro or 200. I don't own one but I understand the 45-85mm to be generally excellent and I keep hearing that at 45mm the 45-85 is quite a lot superior to the 45 prime, which seems to be less than stellar compared to most of the other P 645 lenses.

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    Re: Pentax 645 zoom lenses

    Ed:

    I have the 45-85 and it's very good. I have the superb 67 55-100mm as well and never use it on the 645D rather than the 45-85, since I can see no real difference in performance.

    Tom

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    Re: Pentax 645 zoom lenses

    As pointed out by others, the FA 45-85mm 645 lens is exceptional, especially in the 45mm-65mm range. Beyond 65mm, image can soften up a bit on the sides and corners. How much it softens depends on individual samples, since there is a lot of variation. Other Pentax 645 zooms are good but none reach the levels of the 45-85mm lens.

    Dave (D&A)

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    Senior Member Ed Hurst's Avatar
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    Re: Pentax 645 zoom lenses

    Thanks to you all! Most useful...

    Dave - is the softening up at the sides and corners on a 645D (with its crop factor) or on film?

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    Re: Pentax 645 zoom lenses

    I have tested the 45-85mm f4.5 and the 80-160mm f4.5 lenses using Imatest. The results can be downloaded here: http://www.sublimelightlp.com/blog. Both of my copies are pretty sharp. One thing I noticed is that both lenses have noticeable field curvature, so the best results are obtained by focus stacking using a program like Helicon Focus, which then yields stunningly good results compared to, say, a Sony a900 or a Canon 1ds Mark III. I prefer this 2-step method vs using primes as it means significantly fewer lens changes in the field, which means much less sensor dirt and fewer sensor cleanings.

    Hope this helps

    Jeff

    -------------------------------------------------------
    Sublime Light Landscape Photography
    www.sublimelightlp.com
    Pentax 645D, FA 645 45-85mm F4.5, FA 645 80-160mm F4.5, FA 645 35mm F3.5

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    Re: Pentax 645 zoom lenses

    Quote Originally Posted by Ed HUrst View Post
    Thanks to you all! Most useful...

    Dave - is the softening up at the sides and corners on a 645D (with its crop factor) or on film?
    Ed, my testing of all the Pentax FA 645 lenses that were ever produced were on the 645D body. As mentioned in the post above, there is field curvature in the FA 45-85mm lens (although not too bad). It is most noticable in the excellent FA 35mm f3.5 645 lens.

    Dave (D&A)

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    Re: Pentax 645 zoom lenses

    I've not been very happy with the zooms I tried on the 645D: 55-110, 150-300, 45-85 (well the 45-85 was okay, but large and heavy). I sold them and have stuck with primes: 35, 75, 120m, 150 (my fav), 200, and 300/5.6. For the gap between 35 and 75, I use the 67 55/4 (latest version) with an adapter.

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    Senior Member Ed Hurst's Avatar
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    Re: Pentax 645 zoom lenses

    Hmmm... It sounds like the system is not well served overall by zooms (although the 45-85 seems like it's good without being earth-shattering). I am close to deciding to stick with my primes. It's a pity, since the camera itself is pretty suitable for rapid, flexible use (multiple, selectable focus points, excellent screen for judging previews, quick autofocus system, nice range of accurate auto-exposure modes, etc.)...

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    Senior Member bensonga's Avatar
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    Re: Pentax 645 zoom lenses

    The 645D is really a terrific camera, but Pentax really needs to up it's game with more new (and high quality) lenses to realize the camera's full potential in the market.

    Gary

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