Method and apparatus for previewing exposed photographic films or the like

US4379632A · kind A · utility

Assignee

• Agfa-Gevaert NV · BE

Inventors

• Hubert Dedden · Bitburg, DE
• Jurgen Pfingst · Leverkusen, DE

Key dates

• Filing date: Nov 12, 1981
• Grant date: Apr 12, 1983
• Expiry date: Nov 12, 2001

Classification

• Technology area (CPC G): Physics
• CPC primary: G03B27/80
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

Successive frames of spliced-together exposed and developed photographic films are examined prior to introduction into a copying machine to prevent the reproduction of film frames having blurred images. Portions of or entire film frames at an examining station are spot scanned, line-by-line, and the resulting video signals are processed to determine one or more quotients which denote the ratio of maximum density gradient to density range of the respective film frames, the ratio of first and second density gradients obtained on scanning the entire frequency spectrum or the lower density portion of a film frame, and the ratio of frequency of occurrence of the first and second density gradients. Such quotient or quotients are compared with a threshold value and the results of comparison are used to classify the film frames as suitable or unfit for the making of reproductions.