According to the recent studies on the noise character of photographic materials, two kinds of noise can be defined: the macronoise, σ
D (mac), and the micronoise, σ
D (mic). The macronoise is equivalent to the KMS-granularity of the photographic material, which is defined as
and is belived to include the effect of large-scale nonuniformity of the emulsion layer. On the other hand, the micronoise, which is defined as
is thought to be determined by the ultimate limit of the statistical fluctuation in the process of photon recording on the emulsion layer. This was verified experimentally and also by computer simulation. The results show that σ
D (mac) is generally greater than σ
D (mic), and the standard correlation coefficientis r=1-σ
D2(mic)/σ
D2(mac) greater than zero. This is apparently not due to the overlaping of the successive sampling spots. When the sampling rate was reduced from 50s
-1 to 11s
-1, which is equivalent to increase the distance between the successive sampling spots from 4.4 microns to 190 microns, the micronoise became close or equal to the macronoise, whereas the latter remained unchanged. The computer simulation showed that the micronoise approaches the macronoise as the distance between the successive sampling spots increases. The authors suggested that the macronoise, i.e. the RMS-granularity, can be used as a figure of merit in the evaluation of photographic materrials, whereas the micronoise may be more meaningful when one ’s interest is on the influence of silver halide emulsion on the photographic image quality. The standard correlation coefficient may serve as a measure of the effect of large-scale nonuniformity of a photographic layer.
