Problem with focus

Discussion in 'Exposure Discussion' started by martellsv, Sep 23, 2012.

  1. martellsv

    martellsv Member

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    Hello, i have a problem with my SL66, when occasionally don´t use the tripod in Portraits 6x6 and 6x4.5 format, 80mm Lens and 150mm Lens usually.
    I focus the eye, but in the enlarger/print there is another focus... (a read B. Thornton)
    I am not sure what is the rule with this camera.

    I can post a photo if neccesary. Thanks
     
  2. antmar

    antmar Member

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    Please check if the focusing screen is mounted correctly, if not this is a common symptom.
     
  3. RalphLambrecht

    RalphLambrecht Subscriber

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    this is indeed the most-likely culprit!
     
  4. brucemuir

    brucemuir Member

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    Are you using focus/recompose?
    Focus on eye with a central split rangefinder/microprism screen the recomposing the shot after you have achieved focus?

    If you use wide apertures this technique can cause slight back focus.
     
  5. markbarendt

    markbarendt Subscriber

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    If you can get good focus with the camera on a tripod, it isn't your focus screen.

    That the problem is occasional and hand held suggests that you or the subject simply moved a bit. This is normal, not a gear issue.
     
  6. martellsv

    martellsv Member

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    I use a Maxwell Screen

    I use a Maxwell Screen, Hi-Lux Brilliant Matte... is has no circle no microprism... no reference to focus...

    Please, could you see My gallery (a have only one photo jajajaja) this photo is the example and the problem

    Could be, but i don´t know how check it, (apparently correct except i cannot distinguish the fresnel side)

    f/4. 1/60 I read from rollei SL66 users a recomendation to focus tip of the nose...

    Thanks a lot
     
  7. markbarendt

    markbarendt Subscriber

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    Do you get proper focus on the tripod?
     
  8. markbarendt

    markbarendt Subscriber

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    Your gallery hasn't got any photos I can see.

    Why do they suggest this?

    I find it tough to believe that all SL66's focus improperly. To me that sounds like an urban legend or rule of thumb rather than sound advice.
     
  9. markbarendt

    markbarendt Subscriber

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  10. Gerald C Koch

    Gerald C Koch Member

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    What you are refering to is called the chemical focus and it was a problem when enlarging papers were only sensitive to the shorter wavelengths of the spectrum (violet and blue light). It is not a problem with film which is panchromatic in its response.
     
    Last edited by a moderator: Sep 23, 2012
  11. jnanian

    jnanian Advertiser Advertiser

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    if you are focusing with a tripod and everything is fine
    and hand held it is slightly out of focus, at f4, it seems that
    you have moved, or your subject has moved, ( or both ) so your focus
    is a little off ... this is the same problem a lot of people have with LF ...
    especially when one has to focus, stop lens down, insert film, pull dark slide
    and make the exposure ( and the camera is usually on a tripod ) ...
    maybe rollei suggests focusing on the nose to compensate for people moving forward
    just a tiny bit, when someone is taking their portrait ...


    john
     
  12. fotch

    fotch Member

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    That is a rather heavy camera to hand hold and shoot, at low shutter speeds. If photos are sharp on a tripod, then it is not a camera problem, rather, it is a photographer problem. JMHO
     
  13. martellsv

    martellsv Member

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    IMHO, It could be camera digital reproduction excessive focus not a lot, and the lith help sommthing
    I usually have the same problem, exactly out of focus the defocus distance.... i don´t know how focus tha subject
    to be sure tha exposure is ok, nowdays is a lottery ... always the same error
    this is a headache...

    NOw i am sure i have no problems with the screen, it´s correct thanks a lot J.

    any recomendations? this afternoon i will try again, with my son, same conditions
     
    Last edited by a moderator: Sep 24, 2012
  14. ic-racer

    ic-racer Member

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    When the film bulges in the film gate the focus will shift behind the subject.
    You can confirm if the is the problem by taking the lens off and exposing at "B" with film in the film gate. When you touch the tip of a pencil to the film it should not move if it is against the pressure plate. If you see the film move or indent when touched with the tip of the pencil, the film is bulging.

    The cure for this is to shoot 4x5 film :smile: That is what I do when I don't want to be bothered by rollfilm flatness.
     
  15. RalphLambrecht

    RalphLambrecht Subscriber

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    please elaborateon'chemical focus!
     
  16. E. von Hoegh

    E. von Hoegh Member

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    Early plates were sensitive to blue-to-UV light. These wavelenths of light come to a different point of focus than the greenish wavelengths the eye is most sensitive to. So there was a visual focus and a chemical - sometimes called actinic - focus with the early non-achromatic lenses.
    In diminishing wavelength (or increasing frequency) the colors of light are (infrared)red-orange-yellow-green-blue-indigo-violet(ultraviolet).
     
    Last edited by a moderator: Sep 25, 2012
  17. Doremus Scudder

    Doremus Scudder Member

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    Ralph,

    It's a combination of two things. Some paper's sensitivity to UV and some lenses inability to focus UV at the same plane as other colors in the visible spectrum (which we use to focus).

    Ctein elaborates on this in his "Post Exposure."

    This was more of an issue in the past, and one of the reasons that blue filters came with some grain-focusing devices; by focusing on with blue, you'd be closer to the focus of the UV.

    Nowadays this is rarely an issue: most lenses are better corrected and most papers are no longer so sensitive to UV. Plus, if one stops down a bit, which seems to be the practice more now than in the past, since papers are faster, you get a considerable depth of focus at the enlarging easel which alleviates this effect.

    FWIW, I don't think the OP's problem has anything to do with chemical focus. Likely just difficulty hand-holding.

    Best,

    Doremus


    www.DoremusScudder.com
     
  18. martellsv

    martellsv Member

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    I was using SL66 and "45 degree prism"f/4 1/60 with a magazine 6x4.5 TMAX 100, and not the usual Waist Level and 400 ISO, dificult to get sharpness, precision ... with focus at some situation, portrait with SL66 and "45º degree" i don´t like Likely with hand-holding.

    of course ... waist level is far better, it could help a 400 iso film and not 100... thanks
     
  19. martellsv

    martellsv Member

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    I was using SL66 (the camera about three kgrs.) and "45 degree prism"f/4 1/60 with a magazine 6x4.5 TMAX 100, and not the usual Waist Level and 400 ISO, dificult to get sharpness, precision ... with focus at some situation, portrait with SL66 and "45º degree" i don´t like Likely with hand-holding. IMHO waist level is far better, it could help a 400 iso film and not 100... thanks