Performance of high speed emulsions for color film

A photographic element comprises a support bearing a cyan dye image-forming unit comprising at least one red-sensitive silver halide emulsion layer having associated therewith at least one cyan dye-forming coupler, a magenta dye image-forming unit comprising at least one green-sensitive silver halide emulsion layer having associated therewith at least one magenta dye-forming coupler, a yellow dye image-forming unit comprising at least one blue-sensitive silver halide emulsion layer having associated therewith at least one yellow dye-forming coupler, wherein at least one of said emulsion layers comprisesa) an emulsion with 3D, core/shell grains of at least 0.40 mum average diameter having a high iodide content in the core of the grain with a shell containing a lesser amount of iodide,b) a one-equivalent image-dye forming coupler, andc) a fragmentable electron donating compound of the formula: X-Y' or a compound which contains a moiety of the formula -X-Y';whereinX is an electron donor moiety, Y' is a leaving proton H or a leaving group Y, with the proviso that if Y' is a proton, a base, beta-, is covalently linked directly or indirectly to X, and wherein:1) X-Y' has an oxidation potential between 0 and about 1.4 V; and2) the oxidized form of X-Y' undergoes a bond cleavage reaction to give the radical X. and the leaving fragment Y'; and, optionally,3) the radical X. has an oxidation potential