彩色负片印片颗粒指数的准确测定

分析了彩色负片印片颗粒指数σper实际测试中不同性能负片的测试特点和影响因素。印片颗粒指数的测试点应根据彩色负片的感光特性确定，为正常扩印时对应正片0．74中灰密度的负片密度点。影响印片颗粒指数值的两个主要因素是彩色相纸的反差修正系数α和彩色负片的覆盖力系数ECP；建立了α和ECP的实验求取方法，并通过对几种负片参量的实际测定，分析和说明了参量变化对印片颗粒指数数值的影响程度和应进行的修正。

Accurate Measurement of Print Grain Index of Color Film

The properties of the color film and the affecting factors when measuring the print grain index value have been analyzed. The film measuring point of print grain index should be made according to its light-sensitive characteristics, being the density corresponding to the 0.74 gray density of color paper when printing; the two main factors affecting print grain index accuracy are contrast amendment factor a of the color paper and cover power efficiency E CP of the color film. The methods of obtaining a and E CP are found, and these two efficiencies of several films have been measured. Finally, the print grain index amendment arousing from the variation of a(E CP) is calculated.