Prevention of fog formation in color photographic process

In a process of forming photographic images by processing an imagewise exposed and color developed photographic element comprising a support having at least one photographic layer with an image-wise distributed material possessing a catalytic activity thereon with a photographic processing solution containing at least a cobalt (III) complex having a coordination number of 6 in the presence of a primary aromatic amine developing agent, the improvement which comprises preventing the formation of fog on the photographic images by contacting the photographic processing solution with one side of a fine open-cell porous diaphragm having a mean pore size of 0.1 to 1000 microns of a hydrophobic material comprising higher than 50% polytetrafluoroethylene content, the other side of which is in contact with an aqueous acid solution having an acid concentration of about 0.001 to 10 mol/l, whereby fogging components are removed from the processing solution into the acid solution through the porous diaphragm.