Process for accelerating the precipitation of a low coefficient of variation emulsion

Claim 1

A process of accelerating the preparation of a photographic emulsion containing tabular silver halide grains exhibiting a reduced degree of total grain dispersity comprising providing a dispersing medium containing halide ions consisting essentially of bromide ions, forming in the dispersing medium a population of silver halide grain nuclei containing parallel twin planes, ripening out a portion of the grain nuclei, and growing the remaining silver halide grain nuclei containing parallel twin planes to form tabular silver halide grains, WHEREIN the twin planes are formed in the silver halide grain nuclei within the pAg and temperature boundaries of Curve A in FIG. 1 and a polyalkylene oxide block copolymer surfactant is introduced into the emulsion, introduction being delayed until after the silver halide nuclei containing twin planes have been formed, but introduction occurring before 25 percent of the total silver used to form the emulsion has been introduced, the surfactant being chosen from the class consisting of (a) polyalkylene oxide block copolymer surfactants comprised of at least two terminal lipophilic alkylene oxide block units linked by a hydrophilic alkylene oxide block unit accounting for from 4 to 96 percent of the molecular weight of the copolymer and (b) polyalkylene oxide block copolymer surfactants comprised of at least two terminal hydrophilic alkylene oxide block units linked by a lipophilic alkylene oxide block unit accounting for from 4 to 96 percent of the molecular weight of the copolymer.