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System for Dynamic Matching to Film

IP.com Disclosure Number: IPCOM000091948D
Original Publication Date: 1968-Jul-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Ett, AH: AUTHOR [+2]

Abstract

In retrieving information from photographic film, the accuracy of data retrieval is increased by varying the dynamic gray scale encoding range of the film reader as a function of the dynamic range of the film to be read. In drawing 1, a photographic film image having a density range A is electronically expanded to a range B. In this manner, all film is read as if having a full density range from white to black. Adjustments for offset and gain are performed by a digital computer. Initially, areas of interest in the film frame are scanned. The minimum and maximum gray levels are determined with nominal offset and gain settings. Then under computer control through D-A converter 10, drawing 2, offset adjusting circuit 20 sets the lightest gray level to the equivalent of white.

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System for Dynamic Matching to Film

In retrieving information from photographic film, the accuracy of data retrieval is increased by varying the dynamic gray scale encoding range of the film reader as a function of the dynamic range of the film to be read. In drawing 1, a photographic film image having a density range A is electronically expanded to a range B. In this manner, all film is read as if having a full density range from white to black. Adjustments for offset and gain are performed by a digital computer. Initially, areas of interest in the film frame are scanned. The minimum and maximum gray levels are determined with nominal offset and gain settings. Then under computer control through D-A converter 10, drawing 2, offset adjusting circuit 20 sets the lightest gray level to the equivalent of white. Also under computer control through digital switching circuit 30, the output of circuit 20 is amplified to a value equivalent to range B by gain adjusting circuit 40. The actual value of range B is determined by the input limits to A-D converter 50. The output of A-D converter 50 is then processed in the digital computer.

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