Most, if not all, old technology negative film emulsions had many unintentionally created edge dislocation sites (and other crystalline defects) internally and sulfur sensitization was performed on the surface of the crystal. Because multiple sensitivity centers are present, the emulsion had both internal and surface sensitivity. That is, photoelectrons may migrate to one of many sensitivity centers. In order to exploit the maximum sensitivity of such emulsions, it is generally considered that the developer must have some silver halide solvent action to make the internal latent image sites accessible. Many modern negative emulsions introduce a layer just under the crystal surface where a sufficient number of edge dislocations are intentionally created, while maintaining the bulk of the crystal interior defect-free. Chemical sensitization (e.g., sulfur plus gold sensitization) is applied on the surface. As a result, the photoelectrons are concentrated to a few sensitivity sites on or very near the crystal surface, thereby greatly enhancing the efficiency with which the latent image is produced.