Process of preparing a tabular grain silver bromoiodide emulsion and emulsions produced thereby

Claim 1

A process for the preparation of a silver bromoiodide emulsion comprising providing a host emulsion comprised of a dispersing medium and silver bromide grains optionally including iodide in which greater than 50 percent of the total grain projected area is accounted for by tabular grains satisfying the relationship ECD/t.sup.2 >25 where ECD is the mean effective circular diaemter in μm of the tabular grains t is the mean thickness in μm of the tabular grains and forming silver bromoiodide laminae on the major faces of the tabular grains, characterized in that (a) the silver bromoiodide laminae are formed on the major faces of the tabular grains with an iodide content higher than that of the host emulsion and at least 5 mole percent, based on silver precipitated during this step, and (b) within the pAg and temperature boundaries defined by Curve A in FIG. 1 bromide is deposited on the silver bromoiodide laminae as a silver salt with any additional iodide supplied to the emulsion during this step being limited to less than 5 mole percent, based on silver introduced during this step.