Abstract

Further study is made of the statistical correlation between the <i>density scales</i> of negatives and the <i>sensitometric exposure scales</i> 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 <i>useful exposure scale</i> is abandoned and the terms <i>sensitometric exposure scale</i> and <i>transition point index</i> 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 <i>scale indices</i>. Reasons are given why the <i>contrast</i> of photographic paper is not suitable as a basis for deriving grade numbers. For specifying the shapes of the <i>D</i>-log<i>E</i> 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.

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