Water-soluble substantially non-hardening aldehydes or water-soluble substantially non-hardening aldehyde precursor compounds are suitable as fog-reducing compounds for the photographic dye diffusion transfer process in which an imagewise-exposed color photographic recording material containing light-sensitive silver salt and a non-diffusing dye-releasing compound in at least one binder layer arranged on a layer support, is developed, preferably under the effect of heat, to produce a diffusible dye image and in which the diffusible dye image is transferred to an image receptor layer.