Process of preparing a reduced dispersity tabular grain emulsion

A process of preparing a photographic emulsion containing tabular silver halide grains exhibiting a reduced degree of total grain dispersity comprising

• forming in the presence of a dispersing medium a population of silver halide grain nuclei containing parallel twin planes,
• ripening out a portion of the silver halide grain nuclei, and
• growing the silver halide grain nuclei containing parallel twin planes remaining to form tabular silver halide grains,
• characterized in that
• (a) prior to forming the silver halide grain nuclei halide ion consisting essentially of bromide ion is present in the dispersing medium and,
• (b) at the time parallel twin planes formed in the silver halide grain nuclei, a grain dispersity reducing concentration of a polyalkylene oxide block copolymer surfactant is present comprised of at least three terminal hydrophilic alkylene oxide block units each linked through a lipophilic alkylene oxide block linking unit accounting for from 4 to 96 percent of the molecular weight of the copolymer.