Interactive Enhancement Of Tone Scale

Abstract

The tone scale or gradation of a continuous tone picture is the most important factor related to the quality of an image. We have developed special purpose analog and digital circuitry that enables the real-time (30 updates per second) computation of a tone scale transformation which is then applied to a digitized picture being displayed on a television monitor. In our system the tone scale transformations are controlled by knobs that are labeled in terms meaningful to photographic artisans, rather than requiring an operator to specify points on a transfer characteristic, as is common with other systems. These knobs directly specify minimum and maximum densities, brightness, and shadow, highlight, and overall contrast. These control parameters may be selectively enabled by the operator. After the appropriate aesthetic modifications have been achieved on the television display, the operator may initiate the transformation of the complete stored image prior to subsequent computer processing or hard copy output.