Factors affecting image quality in aerial photography

Thesis (M.A.)--Boston UniversityA laboratory test system was set up to permit the introduction of image degrading factors (haze, vibration, etc.) encountered in aerial photography. This thesis describes the test equipment, procedure and results of each phase, and sets forth some general conclusions in the form of a table of image defects with their possible causes. From the many factors which may affect the image in an aerial negative, several of the more common were chosen for study. These included haze, windows, focus, translatory image motion, vibration, obstruction in the image-forming rays, and variations of exposure and development. The tests conducted were generally of a qualitative nature. The test system consisted of an electronic flash unit with opal diffuser, a positive transparency target, a collimator, a 24-inch f/6 lens, and a focusing-back magazine with vacuum. After determining optimum focus and establishing processing techniques, a negative from the system was obtained to be used as a standard throughout the series of tests. The factors mentioned previously were then introduced into the system one at a time and the resulting negatives compared with the standard. The similarity of many of the effects emphasized the importance of careful analyses of aerial negatives. The advantage of a short exposure time was probably the most outstanding observation made. Although this is not a newly observed fact, the 50 microsecond exposure of the electronic flash unit did emphasize that vibration and other forms of image motion would assume roles of lesser importance if equipment and photosensitive material would permit exposures of shorter duration. After the tests were completed and summarized, it was concluded that the laboratory test method, in the majority of cases, is a reasonable approach to the study of image degrading factors