Simplified test conditions for the evaluation of lenses based on MTF measurements are described, and criteria for interchangeable lenses for 35 mm cameras are proposed. Measurements are to be made for white light, at the infinite conjugate plane, on axis and at 0·7 field (15 mm off axis) positions, at full aperture and ƒ/5·6. The focus is to be adjusted at each aperture so as to give the best MTF response at 30 lines/mm on axis. The MTF responses at 15 and 30 lines/mm are to be examined for the evaluation of the lenses. Simple criteria based on the experimental data for about 100 different types of interchangeable lenses are proposed.