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  1. #11

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    I too think that 25 lp/mm with a 6x9 folder is not bad at all : put that down to 24x36 and you get 60 lp/mm, which is fair ? maybe not absolutely !? but for a prewar folder with a relatively simple lens not coated, I would be satisfied.

    However, maybe it's not only because of the lens. You should test it at all apertures (on the same landscape) and compare the pictures to see if you get decreasing resolution proportional to the aperture or better.

    If you get decreasing resolution proportional to the aperture, then maybe it's not the lens but the mechanical adjustment of the distance to the film (cercles of confusion are proportional to aperture).

    In any case, you should also check with a shoot "full open" if you get the same resolution everywhere, and if not, compare the resolution where it is best to resolution away of this spot. If you get resolution decrease proportional to the distance to max. resolution spot, then maybe you have also a slight misadjustment of the parallelism of the lens to the film plane.

    You see that you might check for a lot of defaults before incriminating the lens. Anyway, your folder should come clean if you see not a lot worse than what you saw at F16, at full aperture. And don't forget that most of the amateur prints in those times were "contacts". It's only with the very good cameras that we have today that we demand huge and however precise enlargments :-)

    Paul

    P.S. I had a Kinax (french folder) that gave me approx. the same results than yours at F16 but could not be used under that aperture, because grossly machanically misadjusted. As it used 620, I did not bother to repair it, and put it simply on the show-shelf :-)
    Last edited by polka; 10-24-2010 at 01:07 PM. Click to view previous post history.

  2. #12

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    I have a better (processed) sample below:


    1. Screen reproduction of full frame scan (800x533px)




    2. 100% crop of 1600spi Epson 2450 scan



    (The leftmost youngster's width at 12x18" / 30x45cm print size would be 0.1" / 2.5mm)

    (TMY2 souped in Pyrocat-MC. Shot hand-held...)


    I'm generally happy with the camera now. Its only problem is the uncoated lens elements; I get some unwanted reflections / ghost images in extremely high contrast areas, when lighting conditions are difficult / extreme. I guess I'll have to improvise a lens hood and carefully select subjects in order to avoid this... BTW, after careful checking, I couldn't find any front standard parallelism or pressure plate problems in the camera.

    Regards,
    Loris.

  3. #13

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    Quote Originally Posted by polka View Post
    ...
    P.S. I had a Kinax (french folder) that gave me approx. the same results than yours at F16 but could not be used under that aperture, because grossly machanically misadjusted. As it used 620, I did not bother to repair it, and put it simply on the show-shelf :-)
    My local technician was talking about this brand, telling me how so good were those cameras and their lenses. Probably it was a newer model that uses 120, though...

    Regards,
    Loris.

    EDIT: Hmmm, according to this page, none of the Kinax cameras were using 120 film. Anyway...
    Last edited by Loris Medici; 10-25-2010 at 10:21 AM. Click to view previous post history.

  4. #14

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    The Bessa 11 was tested in Amateur Photographer Mar 19 1952 .At f/16 the best on axis resolution was 48 lppm.edge 25 lppm.The test was done with HP3 film which limited the maximum resolution to 55 lppm.
    If you are using modern slow speed film for a resolution test higher values would be expected.The test is best done with the focus also set a little more and less than the indicated distance.

  5. #15

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    I was going to ask whether infinity focus had been set correctly on the lens. The Skopar is a Tessar-type with four elements.

    The Tessars that I've used from roughly the same time period have been extremely sharp.

    I have a writeup of a Zeiss Ikon Ikonta 6x9 here.

  6. #16
    Erik Petersson's Avatar
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    Mike Elek, I am impressed by the sharpness you get. I also have a "E-messer" 6x9, but not getting as sharp pictures as I was hoping for. I should probably try it again with
    - tripod
    - high aperture (f11 or so?)
    - try to keep the film stretched

    By the way, how can focusing be checked? Is there anything else I can do to improve results?

  7. #17

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    The lens was collimated and the rangefinder was adjusted by a proficient technician. (Infinity focus and RF is spot on...)

    After some practice and getting used to it, I'm quite happy with the camera - except the fact that I experience occasional problems (flare & ghost images, specifically...) with the uncoated optics, in extreme backlighting situations. I'll improvise a lens hood and select subject matter carefully... I may upgrade to a post-war Heliar mode later!

    See a couple of examples from my latest shooting session below:


    1.1. Full frame, screen size repro:




    1.2. 100% crop of 1600spi scan:




    2.1. Full frame, screen size repro:




    2.2. 100% crop of 1600spi scan:




    - 100% crop images were post processed / optimized for 12x18" (30x45cm) print size.

    - TMY2 in Pyrocat-MC

    - Epson Perfection 2450


    Regards,
    Loris.

  8. #18

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    Not bad, finally ? I think "prewar" folders are a must : such big negs... so easy to carry (in a =large= pocket)... the thrill to have to guess all settings... the focus of (amused) attention you get when shooting...

    and such precise pictures !!!

    Paul
    Last edited by polka; 10-27-2010 at 05:47 AM. Click to view previous post history.

  9. #19
    Erik Petersson's Avatar
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    I will post an example of the low quality I have achieved, as soon as I can. Do you find that the resolution improves much on higher apertures?

  10. #20

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    Loris,

    Did you make the test with the camera hand held or on a tripod?

    If hand held I think 25 lp/mm is excellent for a camera of this type.

    I owned for a while a Bessa II. On a tripod it was capable of 50 lp/mm at f/11. Remember, the lens on this camera is fairly long so any shake or lack of absolute focus is going to reduce resolution.

    Sandy

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