Autocorrelation and Granularity Part I Theory*

Abstract

The applicability of time-series analysis to microphotometer traces is developed with particular reference to two proposed measures of photographic granularity. It is shown that two equivalent functions may be obtained from a microphotometer trace—a correlogram and a power spectrum—and that both Selwyn’s measure of granularity depending on density dispersion σD, as well as Jones and Higgins’s measure depending on syzygetic density difference 〈SΔD〉Av, are directly related to these functions. The conditions under which these measures are equivalent are pointed out.