Abstract: There is described a method of preparing a silver halide emulsion wherein the silver halide crystals are of the twinned type which comprises the steps of (a) forming or providing in a colloid dispersing medium silver halide crystals containing at least 90 mole % iodide, at least 90% of which are of the hexagonal lattice structure with a mean thickness of less than 0.

Abstract: There is described a method of preparing a silver halide emulsion wherein the silver halide crystals are of the twinned type which comprises the steps of (a) providing in a colloid dispersion medium silver halide crystals containing at least 90% iodide and at least 80% of which are hexagonal lattice structure with each displaying predominantly a single basal face, (b) mixing in the dispersing medium containing the sail silver iodide crystals an aqueous solution of an alkali metal of ammonium bromide or chloride (or mixture thereof) so forming twinned silver halide crystals containing iodide and/or the halide or halides being added, optionally (c) adding a silver halide solvent to the dispersing medium and so causing the growth of the twinned silver halide crystals, and optionally (d) then causing the twinned crystals to increase in size by adding to the colloid dispersing medium further aqueous silver salt solution and further alkali metal or ammonium halide and then finally optionally (e) removing the water-

Abstract: Compounds of the formula ##STR1## where A represents the atoms necessary to complete a benzoxazole or naphthoxazole ring which is optionally substituted, R.sub.1 and R.sub.2 are each alkyl, hydroxyalkyl or alkoxy alkyl groups wherein the alkyl moiety comprises 1 to 4 carbon atoms, R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are each hydrogen atoms or alkyl groups having 1 to 4 carbon atoms or phenyl groups, and X is an anion.

Abstract: A method of preparing photographic silver iodobromide or iodochloride emulsions the silver halide crystals of which are of the twinned octahedral or cubic type, which emulsions have improved homogeneity of iodide content and controlled size distribution of the crystal grains, comprising the following steps: (a) forming a colloid dispersing medium silver halide crystals containing at least 90 mole % iodide these said crystals being predominantly of the hexagonal lattice structure, (b) mixing in the dispersing medium containing the said silver halide crystals an aqueous solution of a silver salt and an aqueous solution of an alkali metal or ammonium halide so forming twinned silver halide crystals containing iodide and the halides being added, the rate of addition of silver salt and alkali metal or ammonium bromide being so controlled that the silver halide crystals formed in this step are predominantly twinned and optionally (c) then causing the twinned crystals to increase in size by adding to the colloidal d

Abstract: A method of preparing photograhic silver iodide, containing emulsions is provided.

Abstract: A method of preparing photographic silver iodobromide or iodochloride emulsions the silver halide crystals of which are of the twinned octahedral or cubic type, which emulsions have improved homogeneity of iodide content and controlled size distribution of the crystal grains, comprising the following steps:(a) Forming a monosized silver iodide dispersion in gelatin;(b) Mixing in the silver iodide dispersion aqueous solutions of silver nitrate and alkali metal or ammonium bromides or chlorides in order to form twinned crystals;(c) Performing Ostwald ripening in the presence of ammonia solution and a controlled silver ion concentration to increase the size of the twinned crystals and dissolve any untwinned crystals;(d) Optionally increasing the size of the twinned crystals by the further addition of silver and halide ions; and(e) Chemically sensitising the emulsion.The new photographic emulsions exhibit a high covering power and contrast on development.