Geometry of Low-dimensional Manifolds: An introduction to polyhedral metrics of non-positive curvature on 3-manifolds

The photographic printer of the present invention stores measured gamma values for the photosensitive medium upon which prints are to be made. The gamma values modify exposure times so that the operator button corrections always correspond to a known increment in density. When the photosensitive medium is changed, new gamma values are entered and the printer again modifies exposure times by the appropriate amount so that button correction increments remain constant despite the change in paper gamma.