Silver halide emulsion

A silver halide emulsion which has been subjected to chemical ripening using a labile tellurium sensitizer and/or a labile selenium sensitizer in the presence of at least one compound represented by formula (I), (II) or (IV):

• ##STR8## wherein R'.sup.1 represents a hydrogen atom or an alkyl group having from 1 to 6 carbon atoms;
• m re. presents 0 or 1, when m is 1 and is 1, 2 or 3, Z represents a condensed benzene ring to which R'.sup.2 is substituted and when m is 0 and n is 1 or 2, R'.sup.2 is substituted to the 4- or 5-position of the thiazolium ring;
• R'.sup.2 represents an alkyl, alkenyl, alkyoayl or alkoxy group having from 1 to 6 carbon atoms, or an electron-withdrawing group and when n represents 2 or more, a plurality of R'.sup.2 groups may be the same or different or R'.sup.2 groups may be combined with each other to form a condensed ring;
• R'.sup.3 represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group or an aralkyl group having from 1 to 6 carbon atoms;
• X.sup.- represents an anion;
• and n represents 0, 1, 2 or 3 when m is 1 and n represents 0, 1 or 2 when m is 0;
• with the proviso that the thiazolium ring of formula (I) may be an open ring;
• ##STR9## wherein R.sup.1 represents an aliphatic group, a phenyl group or a naphthyl group;
• M represents a hydrogen atom or a cation;
• and R.sup.4, R.sup.5, R.sup.6, R.sup.7, R.sup.8, R.sup.9 and R.sup.10 each represents a hydrogen atom, an aliphatic group, an aromatic group or COOR.sup.11 wherein R.sup.11 represents a hydrogen atom or an aliphatic group and R.sup.5 and R.sup.6 or R.sup.7, R.sup.8, R.sup.9 and R.sup.10 may be combined with each other to form a ring.