Flat field lens on DSLR

Discussion in '35mm Cameras' started by D Mac, May 25, 2006.

  1. D Mac

    D Mac Guest

    There's been a fair bit of action amongst 5D/1D owners recently in buying up
    old wide angle lenses with very generous field of coverage. And for good
    reason too. The don't vignette and distort like the Canon variations do.

    Well, I've been photographing painted art (digitising paintings) for some
    relatively unknown Aussie artists recently in the lead up to making canvas,
    reproduction prints. This exposes camera equipment designed for 3D subjects
    to all it's weak points. The lenses available from Canon are just one. The
    ideal lens is a flat field lens. I paid a heap for a 50/2 Summicron lens and
    took it back for a refund when it didn't live up to it's reputation. Don't
    get me wrong, the lens is fine on 3D subjects, just not so good when the
    field is flat.

    Then I had a local micro engineer machine me up an adaptor for my 5D which
    had a screw thread to take an enlarging lens. I missed on the depth of the
    first one but by using a bit of math I managed to get the second one pretty
    much spot on. I used an adapted focusing rail from my old Mamiya days for
    critical focus.

    The first few frames I took using a Nikor 50mm enlarging lens were better
    than anything I'd used in the "normal" lenses but lacked some colour
    definition. Then I used a 75mm Rodenstock I've had since 1971 which I
    originally used for enlarging 6x7cm negatives. When I die I want this one in
    my coffin!

    It is just about as good as it gets now. The alternative was to spend $30k
    on a scanning back outfit but with a little ingenuity, some very high
    quality parts from the past and patience, I'm very pleased with the results.
    http://www.photosbydouglas.com/art-repro-on-canvas.htm if you'd like to see
    them.
     
    D Mac, May 25, 2006
    #1
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  2. D Mac

    bmoag Guest

    You could have accomplished about the same thing in Photoshop but it would
    not have been as satisfying.
     
    bmoag, May 26, 2006
    #2
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  3. D Mac

    D Mac Guest

    Well, I use Photoshop every day and I disagree with you.
    Photoshop can do a lot and you can probably find a plugin or action for what
    it can't do but it cannot create anything in an image which was never there
    in the first place or repair what was mangled by a lens designed for 3D
    scenes.

    How are you going to compensate for the way the sensor sees blue differently
    than the actual blue made by mixing violet? What about the reds too? How are
    you going to get this right in Photoshop when you no longer have the
    painting for reference? Take a picture of it perhaps? ROTFL.

    Douglas
     
    D Mac, May 26, 2006
    #3
  4. I've often been curious what would happen if an enlarging lens (or slide
    projector lens) was to be used to take photos, rather than just
    projecting them. You can't use a regular camera lens on an enlarger
    because of the lack of flat field focus, so in theory at least, enlarger
    lenses are better than regular camera lenses. I'd be curious to see some
    photos of a regular type subject with this lens configuration.
    Buried with you when you die heh? let me know where so I can turn up
    with a shovel.
     
    Graham Fountain, May 26, 2006
    #4
  5. D Mac

    Norm Dresner Guest

    | The first few frames I took using a Nikor 50mm enlarging lens were better
    | than anything I'd used in the "normal" lenses but lacked some colour
    | definition. Then I used a 75mm Rodenstock I've had since 1971 which I
    | originally used for enlarging 6x7cm negatives. When I die I want this one
    in
    | my coffin!
    |

    I've purchased a Summicron-S enlarging lens on eBay for pretty much the same
    purpose and have adapters for both the Nikon bellows (works on film and
    digital cameras) and the bellows for my old Bronica S2. Another wonderful
    enlarging lens.
    Norm
     
    Norm Dresner, May 26, 2006
    #5
  6. D Mac

    wsrphoto Guest

    Have you tried a true macro lens, such as Nikon's Micro 50mm and 100mm
    lenses? All "true" macro lenses, not macro/close focusing lenses, were
    designed as a flat field lenses. Also, some older normal lenses were
    made a copy lenses with flat field focus planes. In addition, I
    understand Nikon did make some non-macro lenses as flat field lenses
    (not checked but told by Nikon enthusiasts). In addition Minolta made a
    24mm f2.8 VFC lens with variable focus field, concave, flat and convex.
    Good luck.
     
    wsrphoto, May 26, 2006
    #6
  7. D Mac

    Mark Guest

    What about the Carl Zeiss Planar lenses? If I remember correctly the
    name is referring to the flatness of the field. Tell me if I'm talking
    rubbish :)
    Mark
     
    Mark, May 26, 2006
    #7
  8. D Mac

    wsrphoto Guest

    wsrphoto, May 27, 2006
    #8
  9. Just wondering what the colour rendition is like? I tried this many years
    ago, (close-up region only) on slide film, using my 50 f2.8 enlarging lens
    and comparing against my normal X-700 camera lenses. The enlarger lens was
    so different in colour balance, I decided it simply wasn't worth following
    up, but now with custom white balance etc. I'd probably decide differently.
    The lenses were all Minolta; a 50 f2.8 Rokkor CE, and various MF Rokkors
    including the 50 f1.4MD. In the last few days, I've learnt that my 50 f2.8
    CE Rokkor was in fact a rebadged Schneider, which might just explain the
    colour shift.

    --
    M Stewart
    Milton Keynes, UK
    http://www.megalith.freeserve.co.uk/oddimage.htm





    *** ***
     
    Malcolm Stewart, May 27, 2006
    #9
  10. D Mac

    D Mac Guest

    I'm a long way from being a lens expert but the EL Nikor lens I used had no
    colour correction coating. My presumption is (it's a long way from factual
    research) is that these lenses respond to colours originating in the 3000 -
    4000 kelvin range so colours will be reproduced reasonably correctly if the
    lighting when you use one, is in that range. Outside that range, the colours
    may shift due to different wavelength response in different lighting.

    The whole subject is way past my knowledge area and into optical design. The
    Rodenstock I'm using is "colour corrected" whatever that means but it
    produces more vibrant colour when used with a flash than the EL Nikor did. I
    suspect the Minolta lenses you have could be in the same colour rendition
    group as the EL Nikor I used and might surprise you if the light source was
    tungsten and not daylight.

    I am presently waiting on a new lighting source being made for me which uses
    overlapping 6000 Kelvin flouresent lights in a square I will be able to
    adjust the size of. I'll have the camera in the middle and the flouros
    lighting the paintings. This sort of lighting array is becoming common in
    studios... Just add more tubes for more light.
     
    D Mac, May 27, 2006
    #10
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