film thickness vs focus

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.

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

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.

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.