An apparatus for the development of an emulsion coating, especially of a film sheet of a film punched card, with a development chamber which is limited on one side by the emulsion coating and is arranged in the path of flow of fluid(s) for the one part and air for the other, is to be so improved that a minimum possible chemical consumption with optimum development operation ensue. More especially a development chamber of new conception is to be produced. For this purpose the development chamber (22) comprises a gap chamber (37) of rectangular plan of a height (i) of about 0.1 to 1.0 mm. and is limited in relation to a carrier surface, determining the position of the emulsion coating (12), of a frame rib (39) with seal edge (40) by the surface (35) of a heated chamber body (29). The surface thereof is bevelled off at each of the two edges (34) cross ing the flow direction (x) of the fluid(s) to form a side groove (30) extending approximately over the entire height (n) of the chamber body, the bevelled-off edge and the side groove being parts of a flow gap (23, 23.sub.e) of approximately the width (t) of the part of the surface of the chamber body liberated by the s eal edge and being corrected to an inlet (61) and outlet (83) for fluids and air.