Photo Contrast Considerations for Aerial Mapping.

The compilation of accurate and detailed maps from aerial photographs is a highly complex operation which requires the close cooperation of specialized technical groups. The quality of the final product depends on the ability of each group to consider the over-all requirements as well as those peculiar to its own operations. The images of objects on the ground are recorded on the negative in the camera as shades of gray in an inverse ratio to the brightness of the image at the film plane. The ratio factor of the positive image can be controlled by the contrast of the plates and the gamma of the processing. Such things as the type of camera lens, film and photogrammetric plotting equipment may be considered as relatively fixed, whereas flying altitude, exposure, film processing, and diapositive plate contrast may be considered as variables for any particular type of terrain. Author