EFFECT OF THE ILLUMINATION OF THE NEGATIVE ON THE RESOLVING POWER OF A PROJECTION PRINT

Abstract

Axial measurements have been made of the resolving power of photographic projection printing systems. Besides the usual diffuse and specular systems a third system was considered in which the aperture of the projection lens is not entirely filled by the image of the source. If the relative aperture of this system is calculated considering the source image as the entrance pupil of the lens, then at small relative apertures this system has greater resolving power than the other systems. However, there is no advantage in using the third system at small relative apertures. At large to moderate relative apertures there are only very slight differences among the three systems. Diffusion screens placed in a condenser enlarging system may cause considerable reduction in resolving power if the lens was not previously filled by the image of the source. This effect, and also the high contrast that is very frequently present, are thought to be the origin of references in the literature to sharper pictures obtainable with condenser enlarging systems.