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Thread: Pentax 25mm f/1.4 C-mount seems to be very popular lately...

  1. #51
    Member laptoprob's Avatar
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    Re: Pentax 25mm f/1.4 C-mount seems to be very popular lately...

    First trial of the Pentax 25/1,4. No adapter yet, so handheld with a metal disc. I'm excited, no vignetting! No swirls either. Only the cateye-deformed circles, which seem to be native to fast lenses.
    No mount means very difficult focusing. So out-of-focus tested, very nice!
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  2. #52
    Abbazz
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    Re: Pentax 25mm f/1.4 C-mount seems to be very popular lately...

    Quote Originally Posted by laptoprob View Post
    Only the cateye-deformed circles, which seem to be native to fast lenses
    In fact, they are native to fast lenses with insufficiently dimensioned front element -- it's optical vignetting.

    I am quite surprised your Pentax doesn't exhibit dark corners. Are your pictures full size 4:3 captures?

    Cheers!

    Abbazz

  3. #53
    Member laptoprob's Avatar
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    Re: Pentax 25mm f/1.4 C-mount seems to be very popular lately...

    I set my GF1 to 2:3 ratio, but that difference is small. These pics are full size direct jpegs. The ring I used to handhold this lens in front of the camera has a recess of about 2,5mm, so that should be almost the same as a proper C-mount adapter.
    About optical vignetting, I know this effect from many examples of fast lenses. To get rid of it, the front lens must be huge.
    "You live and learn; at any rate you live" (Douglas Adams)

  4. #54
    Abbazz
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    Re: Pentax 25mm f/1.4 C-mount seems to be very popular lately...

    Quote Originally Posted by laptoprob View Post
    I set my GF1 to 2:3 ratio, but that difference is small. These pics are full size direct jpegs. The ring I used to handhold this lens in front of the camera has a recess of about 2,5mm, so that should be almost the same as a proper C-mount adapter.
    The Pentax 25/1.4 exhibits black corners when used in 4:3 aspect ratio. Switching to 2:3 is enough to get rid of them.

    Quote Originally Posted by laptoprob View Post
    About optical vignetting, I know this effect from many examples of fast lenses. To get rid of it, the front lens must be huge.
    Huge, you are right. Just have a look at the size of the front element of the Sigma 50/1.4 -- which was specially designed to avoid optical vignetting -- compared to the Canon, Nikon and Pentax 50/1.4 lenses:


    Photo credit: DPReview

    Cheers!

    Abbazz

  5. #55
    Member laptoprob's Avatar
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    Re: Pentax 25mm f/1.4 C-mount seems to be very popular lately...

    Ha! got the C-mount adapter today. Great! The 25/1,4 starts vignetting only at 5,6. So there is some room for stopping down.
    I do want a hood for it though. But vignetting will probably start earlier. Grmbl.
    Last edited by laptoprob; 20th November 2009 at 08:57.
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  6. #56
    Senior Member f6cvalkyrie's Avatar
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    Re: Pentax 25mm f/1.4 C-mount seems to be very popular lately...

    Quote Originally Posted by f6cvalkyrie View Post
    I just ordered one, thanks for the link !

    Rafael

    Well, the lens took terribly long, but I finally got it yesterday
    I went for a walk with it today. The pictures came out as a complete surprise to me : this lens performs almost the same as my c-mount Bell&Howell 25/1.9

    Same "ancient" look to the pics, same vignetting, same swirly bokeh.

    Here's a few shots from today. I processed them in accordance with the "vintage" look they anyhow induce.











    All G1 with Cosmicar/Pentax 25/1.4 @ 1.4

    C U,
    Rafael
    E-M1/GH2/G1 Full Spectrum & lots of lenses
    http://www.flickr.com/photos/f6cvalk...th/9226689839/

  7. #57
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    Re: Pentax 25mm f/1.4 C-mount seems to be very popular lately...

    Quote Originally Posted by f6cvalkyrie View Post



    Well, the lens took terribly long, but I finally got it yesterday
    I went for a walk with it today. The pictures came out as a complete surprise to me : this lens performs almost the same as my c-mount Bell&Howell 25/1.9

    Same "ancient" look to the pics, same vignetting, same swirly bokeh.

    Here's a few shots from today. I processed them in accordance with the "vintage" look they anyhow induce.


    All G1 with Cosmicar/Pentax 25/1.4 @ 1.4

    C U,
    Rafael
    Wonderful moody shots, Raf. I have this lens, need to do more with it

    Keith

  8. #58
    Senior Member f6cvalkyrie's Avatar
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    Re: Pentax 25mm f/1.4 C-mount seems to be very popular lately...

    Thanks, Keith.
    This seems to be a very moody lens

    Here's two more shots with it, wide open, and a little PP done


    (in the dark forest)



    (steep hill)

    CU,
    Rafael
    E-M1/GH2/G1 Full Spectrum & lots of lenses
    http://www.flickr.com/photos/f6cvalk...th/9226689839/

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