Lens resolution is defined as the number of resolution target lines per millimeter that can be discerned in the film. Discerned means that the individual lines from the target can be seen, however slight and fuzzy. Where the lines cannot be discerned, a (theoretically) 50% gray is observed. The lines are black and the spaces between parallel lines are white and of the same width as the lines. The resolution target is of a standard size and provides lines of various spacing and at various places in the field of view and in various orientations. The target is properly filled by adjusting the camera to subject distance. The math of this geometry is used to translate target lines per millimeter to lines per mm at the film plane. In practice, the measurement is made using high power loupes examining (properly exposed and developed) high resolution, high contrast film. There is no hard standard for the film used and different labs use different films and different targets have "blacker" blacks" and "whiter" whites. There is an Air Force standard target which is often used, but often folks use replicas of this target. This means that the observed resolution varies from lab to lab, person to person. Therefore, do not compare the results of one lab with another, or one persons measurement with another.
Regards, Bob... -------------------------------------------- "Do not suppose that abuses are eliminated by destroying the object which is abused. Men can go wrong with wine and women. Shall we then prohibit and abolish women?" -Martin Luther From: "Anders Hultman" <[EMAIL PROTECTED]> > I've seen people here talk about the resolution of lenses. I fully > understand the physics behind resolution of both digital image > sensors and film, but what really is resolution when talking about > lenses?
