Abstract

The developability of some latent-image centers can be destroyed by the absorption of infra-red radiation (Herschel effect). Absorption of one quantum per center is sufficient to destroy the developability of some centers, indicating that the removal of one silver atom or F-center is sufficient to destroy the developability of such a center. Experiments have been carried out on motion-picture positive film to determine whether the developability of such centers can be restored by any of the various known methods of latensification. Experiments were also carried out to determine what effect latensification prior to the infra-red exposure has upon the Herschel effect. Both physical and direct development were employed. The degree of stabilization attained when latensification preceded infra-red exposure was calculated in terms of percent difference between the change of density of the control and of the latensified film. The degree of restoration attained when latensification followed infra-red exposure was calculated in a similar way. All latensifying agents investigated except perborate caused either partial or complete stabilization for both direct and physical development. Perborate treatment prior to infra-red exposure increased the Herschel effect. Gold and mercury produced increased infra-red sensitivity. Of the agents studied, only low intensity light and water showed any restoration for physical development. For complete direct development, no restoration was observed except for bisulfite which produced total restoration. These results indicate that, with the exception of bisulfite treatment, latensification procedures will not make developable any significant number of subimage centers which originally were smaller by one unit than the critical size necessary for initiating development.

© 1950 Optical Society of America

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