Photographic systems used in the Apollo program for photometric data reduction require more precise methods of photometric calibration than are used to determine the nominal operating parameters. A technique for more precise photometric calibration of cameras is described. This involves the determination of the absolute magnitude and spatial variation of illuminance in the image plane of a camera as a function of the nominal operating parameters such as f-stop. The method involves photographing an artificial scene of known, luminance which has the same approximate color temperature as the object to be photo-graphed. This calibration must be performed at all of the various camera settings. The processed photographs will be scanned by a microdensitameter to analyze the transmission efficiency and the error in calibration of shutters and lenses. By use of this calibration information a determination of scene brightness can be made from image density when using the proper sensi-tometric calibration (density vs. log exposure).