film thickness vs focus

Discussion in 'Minox' started by tony__|2, May 2, 1999.

  1. because of the tiny focal lengths involved, could different film thicknesses actually make a difference in focus? I know I should quit worrying about such insignificant details and just go take pictures, but this technical stuff is interesting.
     
  2. Tony,
    If you are worried about film thickness in a Minox camera, the trouble
    is not from focal length but from mechanical ware caused by thick film
    (over 6 or even 5.5 mils). In all cameras, when film is introduced to
    the pressure plate and pressed into position, it is the emulsion which
    faces the lens. The emulsion thickness on all films can only be
    measured on an atomic scale (fairly large, maybe 30 atoms thick, but
    that's just a guess would appreciate comment) The area that actually
    is chemically changed by the light cannot be more than a few atoms
    thick, whatever the thickness of the film behind it is utterly
    inconsequential as no image is formed there and it thus, not part of
    the focal plane. The only exception to this rule are cameras such as
    the tessina which place the emulsion side away from the lens, but NO
    Minox is designed in this fashion. Also the depth of field is
    extraordinarily large in Minox subminis, any measurement difference of
    one or two ml would be small (though not that small, on the order of a
    foot)
    Good Luck!
    George Maltezos
     
  3. Avoid using thick film in Minox, particular in Minox III/IIIs/B where
    the film plane is curved . <P> Thick film is
    hard to conform to the curved film plane, and the image will not be
    as as sharp.
    <P>Thick film is hazardous to Minox camera and Minox slitter, avoid them like plague.
    <P> As the discussion on "Mid roll change film" pointed out, the coiled up film
    in Minox cassette is like a tensioned main spring in a watch. The thicker the film, the
    thicker the spring, the harder is is to wind the film,; you may exert too much
    too much stress on the film advance mechanism.
     
  4. May I correct your affirmation, George?
    Even Tessina shows the emulsion side towards the lens (better,
    towards the mirror), it could not be the other way since the film is
    not transparent enough before developing and fixing. Tessina films
    are reversed during printing, showing the emulsion towards the
    condenser instead of to the objective.
     

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