Further study is made of the statistical correlation between the density scales of negatives and the sensitometric exposure scales of photographic papers. A formula relating these two variables is proposed, for use as a guide in photographic printing, whereby the density scale of the negative can be used as a means of choosing the grade of paper to be used in making the print. The suggestions of Sanders regarding statistical methods of analyzing the data are discussed. The term useful exposure scale is abandoned and the terms sensitometric exposure scale and transition point index are proposed. It is suggested that the sensitometric exposure scale be adopted as the basis for grading photographic papers and that the new numbers be called scale indices. Reasons are given why the contrast of photographic paper is not suitable as a basis for deriving grade numbers. For specifying the shapes of the D-logE curves of photographic papers, the method proposed by Morrison is recommended. Data are presented on the frequency of occurrence of the various density scales of amateur negatives.
LOYD A. JONES and C. N. NELSON, "Control of Photographic Printing: Improvement in Terminology and Further Analysis of Results," J. Opt. Soc. Am. 38, 897-917 (1948)