The Theory of Halftone Screen Image Formation and its Bearing on Practical Applications

Abstract

Practical halftone photography developed at first almost independently of theoretical considerations, although theory based on geometric optics provided some guide for the practical operator. The “diffraction” theory is reviewed; it now provides a fairly complete explanation of halftone image formation, and has further defined the conditions for practical work.

The techniques required to produce screen negatives and positives with optimum tonal gradation and dot formation for relief and surface printing are discussed. Some techniques have been made possible by the introduction of new types of photographic emulsion.

The development of the “contact” screen is outlined, and the results obtained with available contact and cross-line screens are compared with special reference to the gradation and resolution of the final image.