An Evaluation of Photographic Image Quality and Resolving Power

It is often desirable to express the performance characteristics of electronic and photographic imaging systems in the same terminology. The photographic measures — resolving power, number of perceptible gray-scale steps, granularity and others — are shown to be system properties which can be computed from basic characteristics: the intensity transfer function, sine-wave response function and the noise level. — Following a review of the quantum relations of signal and noise in a two-dimensional image, the concepts of sampling areas and equivalent passbands are introduced to compute the noise spectrum, equivalent grain size and quantum yield of the photographic process. Number and size of the grains in a sampling area are shown to be functions of exposure and amplification (development), which explains the nonlinear relation between optical density and total noise energy obtained with emulsions containing a range of grain sizes. General expressions are derived for calculating the resolving power of an imaging system for specific test objects. — Threshold signal-to-noise ratios and corresponding probabilities for visual detection of 3-bar test objects and intensity steps are determined in Part II, illustrated by numerical examples and observations. — Instrumentation and methods for photoelectric measurement of signals and noise, and in particular, the sine-wave response functions of microscopes, lenses and photographic emulsions, are discussed in Part III of the paper.

Print ISSN

0361-4573

Published

1964-02

Content type

Original Research

DOI

10.5594/J06117