Cinematographic annual : 1931 (1931)

238 CINEMATOGRAPHIC ANNUAL bromide apparently increased the size of grain. Their own work, covering some fifteen developing agents or mixtures of agents, led them to agree in general with the earlier workers, noting, however, in addition that excess of alkali tended to produce a slight enlargement of the grain and that two developing agents, paraphenylene diamine and orthoamidophenol, produced much finer grains than other reducers. Further work of similar nature was planned and published later14. Wallace3 writing about the same time considered that prolonged development increased grain size and, therefore, recommended an active developer compounded to give the contrast desired in relatively short time. Scheffer4 presented photo-micrographs of undeveloped, partially developed and fully developed grains. The pictures show development with filament formation and give much evidence of clumping and irregular grain shapes. Hodgson5 showed results not corresponding to those of Scheffer as, under his conditions, the grains maintained the same shape as that of the original silver bromide, with the exception of such changes as could be ascribed to strains in the gelatine. Later, Davidson10 suggested that Scheffer's results were probably due to too high an intensity of light in making the photographs but found more changes in shape than Hodgson. Svedberg6 found that the size of the developed grain depended upon the original size of the silver bromide particle and the amount of development but not on the exposure. Higson7 stated that the grains resulting from development had closely four times the area that they had when undeveloped. Wightman and Sheppard8 proceeded to show that this conclusion was contrary to previous work of Higson and others. Mees9 considered that the evidence indicated the area of the developed silver grain to be substantially the same as the parent halide grain. Davidson10,11 found in general an increase of grain size on development, the size increase being proportional to the photographic speed of the plate for a group of related emulsions of different speeds. Further statistical study indicated that the size increase depended upon both the emulsion and the developer, being in general greater for the faster emulsions. The nature of the grain deposited appeared different to him in the different developers, slow working developers of the borax type giving a notably spongy grain. Sheppard and Trivelli12 did not feel that the proportionality of size increase and speed could be as exact as Davidson indicated, but gave data of their own showing a size increase greater, in general, for the larger grains. Wightman, Trivelli and Sheppard13 in their extended study of the size frequency distribution of grains in photographic emulsions noted increases of grain size for the larger grains, changes of relative positions of grains in the emulsion during development, and the reduction in size and total disappearance of some of the smaller grains. As has already been indicated, much effort has been spent in attempting to find developing conditions yielding grains of minimum size. A. and L. Lumiere and A. Seyewetz2 noted their intention of further study of developing conditions. As a result of their studies they recommended14 slow development with paraphenylene diamine as the best for fine grain and considered that the borax formula