A Quantum Theory of the Latent Photographic Image

An explanation of the process of photographic exposure on the basis of a true photochemical reaction is offered.. It is pointed out that the apparent failure of the Einstein equivalence law in the case of photographic exposure for short intervals is not real, and an, equation is derived on the basis of the assumption that the absorption of one quantum by a sensitivity center of the grain produces an activated, but unstable state which renders the grain as a whole developable. The assumption that an activated grain may revert to an undevelopable state is an important part of the present theory, and evidence in favor of this assumption is cited. The theory that the photographic process is autocatalytic is criticized on the basis that the point of inflection of the Hand D curve indicated by this theory is much higher than the point found experimentally. A preliminary treatment of the Herschel effect is given on the basis of the proposed theory, and an equation holding under special conditions is derived. The explanation of the intermittency effect as put forward by Blair and Hylan is still valid in the light of the present theory. Data taken from reliable sources are given to show that the general equation holds over wave-lengths ranging from red light to x-rays, and emulsions from Azo to Eastman Portrait.