ground resolution
Original archive entry. The text, images and links below are kept as they were written.
The degree to which an optical or photographic system can reproduce fine detail of the surface being imaged, as measured against a photographic scale. It is the product of a combination of capabilities of the film (graininess, sensitivity, etc.) and the lens (type, resolving, power, etc.) and is usually expressed in line pairs per millimeter. Photographic scale is found by dividing the altitude at which the picture is taken by the focal length of the camera. For Lunar Orbiter, the effective film resolution was 76 line pairs per millimeter, which gave 1-meter resolution through the 610 mm lens and 8-meter resolution through the 80 mm lens under predetermined contrast conditions on the lunar surface.