The camera is thought to have a very poor optical system, such that whenever a spot of light appears on the input plane, it forms a very diffuse Focus onto the photocathode.
Fig. 3.11. “The Magic TV” (a) System (b) Output Plane. Pairs of letters correspond to processing units, labeled by the images of test vectors (with coordinates defined in (c)). (c) Input Plane showing those points to which the various processing units (corresponding to nodes of the net) have become most sensitive
Numerous stereometric optical techniques and moire methods for topographic applications have been devised; these often require complex transformations for data reduction.