Processes are disclosed for incorporating a water-insoluble substance in a diffusion resistant form into a hydrophilic colloidal layer of an element. In a first process A the water-insoluble substance is present during the polycondensation of diol(s) or polyol(s) and carboxylic acids, whereby at least 6 mole % of the reagents bear a water-solubilizing group, preferably a sulpho group in the salt form; the obtained mixture of polyester and water-insoluble substance is then dispersed in an aqueous medium. In an alternative process B the polyester is first prepared and then mixed homogeneously with the hydrophobe substance by melting in a reactor or extruder; the mixture is then similarly dispersed. The obtained latex is then incorporated in a hydrophilic colloidal layer which is coated on a support.The obtained element can serve as base for a reprographic image, e.g. a color proof image, or can form part of a complete photographic material.In a preferred embodiment the water-insoluble substance is a brightening agent.