COLOR PHOTOGRAPHIC DEVELOPMENT ACCELERATORS .5. SELECTIVE DEVELOPMENTACCELERATION OF HYDRAZINE COMPOUNDS 1,3,4-THIADIAZOLE HETEROCYCLIC SYSTEM

Photographic speed can be increased by incorporating selective develop ment accelerators (hydrazine derivatives with adsorbed groups) into se veral types of silver halide emulsion because of the stronger accelera ting action on image development than on fog formation. The developmen t acceleration of the selective development accelerators depends on th e pH of the developer. The higher the pH of the developer, the stronge r the development acceleration of these compounds. When the pH of the developer rises to 12.50, the 'hydrazine effect' (super high contrast and short toe) is obtained. The accelerating action of the selective d evelopment accelerators appears over a wider pH range of developer, wh ereas that of the hydrazine compounds without adsorbed groups occurs o nly at higher pH of the developer (pH > 11.50) under the same experime ntal conditions.