FIELD: photographic chemistry. SUBSTANCE: method involves the controlled two-jet crystallization at constant pBr = 1.0-3.7 and at pH = 3.8-11.2 with simultaneous addition of solution N 2 containing silver nitrate and water and solution N 3 containing potassium iodide, potassium bromide and water to the solution N 1 containing gelatin and water as 2-7 portions at iodide concentration decrease from 0.06-0.40 mole/mole silver in solution N 2 in the first portion of solution N 3 to 0.01-0.06 mole/mole silver in solution N 2, in the last portion of solution N 3 by value 0.01-0.30 mole/mole silver in solution N 2; total potassium iodide content in all portions of solution N 3 consisting of 0.04-0.25 mole/mole silver in solution N 2 and volume of each portion of solvent N 3 consisting of 5-90% of total volume of solution N 3, and simultaneous addition of solution N 4 containing silver nitrate and water and solution N 5 containing potassium bromide and water or potassium bromide, potassium iodide and water to the prepared core emulsion at concentration potassium iodide 0.005-0.05 mole/mole silver in solution N 4, in the presence of (10-2)-(10-7) mole/mole silver in solutions N 2 and N 4 of nitrogen-containing heterocyclic compound of the formula (I): 
where: R1, R2 - H, C1-C5-alkyl. Crystallization is carried in the presence of compound of the formula (I) 
. EFFECT: improved method of preparing. 2 tbl
