| 摘要 |
Tabular grain silver halide emulsions are disclosed containing chloride and bromide in at least annular grain regions. The tabular grains having a thickness of less than 0.5 micron, preferably less than 0.3 micron, a diameter of at least 0.6 micron, and an average aspect ratio of at least 5:1, account for at least 35 percent of the total projected area of the total silver halide grain population. The average molar ratio of chloride to bromide in at least the annular grain regions ranges up to 2:3. The tabular grains containing chloride and bromide in at least annular grain regions are formed by maintaining a molar ratio of chloride and bromide ions of from 1.6:1 to 258:1 and the total concentration of halide ions in the reaction vessel in the range of from 0.10 to 0.90 N during introduction of silver, chloride, and bromide salts into a reaction vessel, thereby favoring the coprecipitation of chloride and bromide in a tabular crystal habit.
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