Direct positive silver halide photographic emulsions

A direct positive silver halide photographic emulsion fogged with light or chemical foggants which contains at least one dimethine spectral sensitizing dye containing a cyano-substituted indolenine ring in molecular structure and represented by the general formula:

• ##STR38## wherein R.sub.1 is a group selected from a lower alkyl, a hydroxyalkyl, an acyloxyalkyl, an alkoxyalkyl, a carboxyalkyl, an alkoxycarbonylalkyl, a sulfoalkyl, an aralkyl, a sulfoaralkyl and an alkenyl, R.sub.2 and R.sub.3 are lower alkyl groups, Z is a group of atoms necessary to complete a nitrogen-containing 5- or 6-membered heteroring which is linked by the 1-, 3- or 4-carbon atom thereof to the dimethine chain, said nitrogen having no substituent or having a substituent selected from the group consisting of alkyl, sulfoalkyl, aryl, aralkyl and alkenyl, X is an acid anion and n is 1 or 2.