<title>Panel Discussion: Materials And Instrumentations</title>

Abstract

First Questioner (not Identified):Mr. McCamy, I would like your comments on aperture size for measuring granularity.Mr. McCamy:If you use too large an aperture you get no variation but a uniform density. If the aperture comes to zero you will either measure no density or a maximum density. So the aperture selected is somewhere in between. Most of our work is done with a 22 micron aperture and Eastman Kodak reports its work at 24 micron apertures. Another comment was that some work was done at a 48 micron square aperture. When you go to very fine grain materials you must go down smaller in your aperture size otherwise you get no information out.Dr. Shepp:In microdensitometry, the wavelength of the probing light is about 0.5p (500nm) and therefore slit widths of ly and less lead to diffraction problems.Post Editorial Note by Mr. Derr: