Photographic emulsions and elements containing agel crystals forming epitaxial junctions with AgI crystals

A photographic gelatino-silver halide emulsion incorporating as a discrete phase, monodispersed radiation-sensitive composite silver halide crystals comprised of

• beta-phase truncated bipyramid silver iodide crystals having a minimum mean diameter of at least about 0.2 micron,
• in each composite crystal at least one silver chloride crystal forming an epitaxial junction with the silver iodide crystal,
• at least half of the facets of the silver iodide crystal being substantially free of epitaxial silver chloride and
• silver chloride being limited to from 1 to less than 50 mole percent, based on the total silver halide forming the composite silver halide crystals.

In a photographic element comprised of a support and, as a coating on the support, a radiation-sensitive emulsion layer including a photographic vehicle as a continuous phase and, as a discrete phase, radiation-sensitive silver halide crystals,

• the improvement wherein at least a portion of the radiation-sensitive silver halide crystals are composite silver halide crystals comprised of
• multi-faceted, radiation-receptive silver iodide crystals having a minimum mean diameter of at least 0.1 micron,
• silver chloride crystals forming epitaxial junctions with the silver iodide crystals,
• at least half of the facets of the silver iodide crystal being substantially free of epitaxial silver chloride, and
• silver chloride being limited to less than 75 mole percent, based on the total silver halide forming the composite crystal.

In a photographic element comprised of a support and, at least one radiation-sensitive gelatino-silver halide emulsion layer as a coating on the support,

• the improvement wherein the radiation-sensitive gelatino-silver halide emulsion layer contains monodispersed composite silver halide crystals consisting essentially of
• beta-phase truncated bipyramid silver iodide crystals having a minimum mean diameter of at least about 0.2 micron,
• in each composite crystal at least one silver chloride crystal forms an epitaxial junction with the silver iodide crystal,
• at least half of the facets of the silver iodide crystal are substantially free of epitaxial chloride and
• the silver chloride is limited to from 1 to less than 50 mole percent, based on the total silver halide forming the composite silver halide crystals.