Opal film

Opal film , also called opal copy , is a special film for the electronic engraving of the printing cylinder in gravure printing . The white-colored layer support made of polyester , which is coated with light-sensitive silver halide , is typical . Silver halides are also used in analog photography because of their sensitivity to light . When exposed to light, the silver cation is reduced to elemental silver and a black and white image is created.

The opal film is a true-to-size material for scanning overhead in the Helio-Klischograph . The opal film with the positive image is optically scanned on the scanning cylinder. Depending on the brightness of the scanned image point, the amount of light reflected is converted into an electrical signal and sent to the engraving system.

From 1995 the signals are processed digitally by the computer . The electromagnetic engraving system is controlled by the computer and a diamond stylus engraves the print image in the copper layer of the printing plate. Today, data is transferred from a digital workflow that usually starts with PDF pages and can be automated as required. The engraving systems read 1-bit Tiff files that are used for scanning.

Mimosa Opalfilm Professional was a special, highly sensitive enlarging material on an opaque film base for the production of black and white images that were suitable for both top and through viewing. The light attenuation by the layer support was about 25%. The front and back were coated; the front of the opal film was glossy, the back was slightly matted.

literature

• Helmut Kipphan (Hrsg.): Handbuch der Printmedien. Springer Berlin, November 2000. ISBN 3-540-66941-8
• Agfa data sheet, Agfa-Gevaert AG, Leverkusen (1971)