Optical viewing systems have been well designed for specific applications. However, partial coherence evaluation of the optical viewer illustrates potential for control of the frequency response to phase and amplitude components of the photographic image (where the phase component is due to the emulsion relief image). The complex image formed by the partially coherent system contains a separable response to the phase and amplitude components for a low contrast object. Optical frequency response control is applied to the complex image by design of a variable source size condensing system and by inserting an attenuation filter in the pupil of the imaging lens. Illustrations are given to show the adaptability of the system response to low contrast images.