The Optimal Meaning of Average Gradient for Photographic Films In Hybrid Photographic Systems with Digital Image Processing

摘要

The main object of this research was the definition of optimal meaning degree of development for photographic films for getting the best characteristics of tone reproduction. The database of tone reproduction parameters of the photographic systems with digital image processing was created on the basis of construction of objective tone reproduction curve and calibration curves. Subsequent scanning negative image was applied. The cameras (Canon F1, Nikon F4, Pentax MZ-6, Pentax MZ-7), the films Kodak T-Max 100, 400, Ilford 100 and the developer D-76 were used in our experiments. The standard gray scale was used as test-object for taking photos. The films were developed up to various average gradient values in the interval 0.55 -0.90 for the definition of optimum development degree. According to the technique, developed by us (the "Mirror" program), the curves of objective tone reproduction have been constructed for all shooting and processing specified conditions. At the same time the image quality was visually estimated up on shooting objects (picture, portrait, landscape etc). The submitted results convincingly confirm necessity of an establishment of different degrees of development for black-and-white still-picture films and movie films. The analysis of objective tone reproduction curves allows to make conclusion, that the optimum meaning of average gradient for photographic films should be in an interval 0.80-0.85.