Principles of cinematography : a handbook of motion picture technology (1953)

16-MM FILMS AND THEIR USES 409 from Diagram 'C to consist of areas of unaltered silver bromide grains, corresponding to the black rectangles in the original subject, interlaced with areas of transparent film base, corresponding to the white rectangles in the original subject. Once the bleaching solution has been thoroughly removed it will be obvious that areas '4\ '5' and '6' will correspond exactly with areas' 1 ', '2' and '3' in the original subject. The film is then given a second exposure so that the silver bromide grains, which remain may then be reduced in a second developing solution and so produce the final result as shown in Diagram 'D\ The film is then fixed and washed in the usual manner. As is well known, the final appearance of a metallic silver image, and particularly the granularity of the image, is related to the size and the distribution of the individual silver grains. The larger the grains are or the more concentrated their distribution becomes the more easily will they react to the developing solution. Because of this the first grains which become fully developed are those larger ones which are more likely to cause the graininess appearance of the image. However, when the film is developed to a positive by the reversal process, the large and highly sensitive grains are all developed up in the first exposure and are subsequently dissolved away in the bleaching process. The resultant pictures are therefore composed of the smaller less sensitive grains and, in consequence, do not appear to have such a grainy structure DO '■','■' .::■■ ORIGINAL SUBJECT FILM AFTER Ist DEVELOPMENT HDEVELOPED METALLIC SILVER U UNDEVELOPED SILVER BROMIDF FILM AFTER BLEACH an on on FILM AFTER 2nd DEVELOPMENT FIXATION WASHED & DRIED FILM Fig. 169. — The stages of reversal processing.