The grain/sensitivity ratio of a photographic silver halide material may be improved by adding a compound of the formula I to one of its layers. The material moreover exhibits a low increase in fog on storage. ##STR1## in which: Y.sub.1, Y.sub.2, Y.sub.3 each mean one of the following residues ##STR2## R.sub.1 to R.sub.34 mean H, alkyl or aryl; two residues (R.sub.1 to R.sub.34) located on the same N atom may complete a 5-, 6- or greater-membered ring containing at least one N atom and optionally further heteroatoms; two residues (R.sub.1 to R.sub.34) located on adjacent N atoms may complete a ring involving both N atoms and at least one P atom;X.sup.- means an anion required to balance the charge, for example Cl.sup.-, Br.sup.- or tosylate (TosO.sup.-).