抄録
In the previous paper (Part 1), a study on the measurement of power spectrum of photographic material was reported. This work was undertaken to determine the autocorrelation function of grain pattern of printed image by using an optical autocorrelator, to obtain the power spectrum of grain pattern with the use of Fourier transformation, and to evaluate each spectrum.
When the picture quality of release cinema positive film and of medical X-ray film are concerned, it is very important to consider the graininess of printed image, Because the image of cinema positive film and of X-ray film are formed by printing with negative film and fluorescent intensifying screens respectively, the grain patterns of these printed images are seriously affected by the grain pattern of negative film and of fluorescent screens. Autocorrelation function of granularity pattern of printed image consists of two components. One of these components, which has shorter correlation distance, corresponds to the grain pattern of positive film or that of X-ray film, and the other corresponds to the grain pattern of negative film or fluorescent screens.
Fourier transform of the autocorrelation function was obtained and then the contribution of each component to magnitude of graininess was determined. When the Fuji cinema positive film is printed with Fuji Neopan SSS film, the contribution of grain pattern of Neopan SSS film was about one hundred times as large in the magnitude of graininess as that of grain pattern of positive film. When the Fuji medical X-ray film is printed with fluorescent screens, the contribution of grain pattern of fine grain fluorescent screens was about three times as large as that of X-ray film and the contribution of grain pattern of coarse grain screens was about ten times as large as that' of X-ray film. The quantitative comparison of two types of screens on graininess was made with the use of this method.
Response function of the printing optical system, which includes spatial frequency characteristic of positive materials and that of printer, was obtained by using the following quantities, the power spectrum of grain pattern of negative film and that of printed grain pattern.
