The optical-reduction method of impressing images on emulsion samples for measuring the resolving power of the latter is preferred over the contact-printing method, chiefly for its practical convenience. A description is given of a camera containing a 150-mm f/5 apochromatic telescope objective, which makes 13 exposures to incandescent light on a power-of-two time scale. For materials of high resolving power, another camera is described that accommodates microscope objectives and makes 7 exposures to monochromatic light on any desired time scale. This camera uses distance pieces to position the sample, and the technique of using such pieces is discussed. The methods of making test objects and the precautions required are described.