Preparation of silver halide tabular emulsions in the presence of non-aqueous polar aprotic solvents and/or protic solvents having a dissociation constant smaller than that of water

Method of preparing tabular silver halide emulsions having a tabularity, defined as a ratio between aspect ratio and thickness of emulsion crystals, of at least 25 and homogeneity of distribution of said silver halide emulsion crystals, defined as a hundred times a ratio between the standard deviation and average projective crystal diameter of said crystals of less than 30, characterized by the steps of

• forming silver halide grain nuclei by introduction of an aqueous silver salt solution and an aqueous halide salt solution, both solutions optionally comprising at least one non-aqueous solvent, in a reaction vessel containing water, a protective colloid and at least one non-aqueous aprotic solvent selected from the group consisting of acetone, dimethylsulfoxide and acetonitrile or a protic solvent selected from the group consisting of methanol and ethanol, having a dissociation constant smaller than that of water in a ratio by weight of solvent versus water from 5 to 60%,
• adding an aqueous silver salt solution and an aqueous halide salt solution to said reaction vessel containing silver halide grain nuclei at a pBr value higher than 2.0,
• flocculating grown silver halide emulsion grains,
• washing and redispensing.