film image. The glass screens were made obsolete by high-contrast films where the halftone dots were exposed with the separation film. This in turn was replaced by a process where the halftones are electronically generated directly on the film with a laser. Most recently, computer to plate (CTP) technology has allowed printers to bypass the film portion of the process entirely. CTP images the dots directly on the printing plate with a laser, saving money, and eliminating the film step. The amount of generation loss in printing a lithographic negative onto a lithographic plate, unless the processing procedures are completely ignored, is almost completely negligible, as there are no losses of dynamic range, no density gradations, nor are there any colored dyes, or large silver grains to contend with in an ultra-slow rapid access negative. Screens with a "frequency" of 60 to 120 lines per inch (lpi) reproduce color photographs in newspapers. The coarser the screen (lower frequency), the lower the quality of the printed image. Highly absorbent newsprint requires a lower screen frequency than less-absorbent coated paper stock used in magazines and books, where screen frequencies of 133 to 200 lpi and higher are used. The measure of how much an ink dot spreads and becomes larger on paper is called dot gain. This phenomenon must be accounted for in photographic or digital preparation of screened images. Dot gain is higher on more absorbent, uncoated paper stock such as newsprint. See also Block printing Flexography Letterpress printing Offset printing Rotogravure Typography References Notes Bruno, Michael H. (Ed.) (1995). Pocket Pal: A Graphic Arts Production Handbook (16th ed.). Memphis: International Paper Gascoigne, Bamber. How to Identify Prints: A Complete Guide to Manual and Mechanical Processes from Woodcut to Inkjet, 1986 (2nd Edition, 2004), Thames & Hudson, Hunt, R.W.G., The Reproduction of Color (1957, 1961, 1967, 1975) Yule, John A.C., Principles of Color Reproduction (1967, 2000) Morovic, J., Color Gamut Mapping (2008) Further reading Bruno, Michael H. (Ed.) (October 2000). Pocket Pal: A Graphic Arts Production Handbook Graphic Arts Technical Fndtn; 18th edition, Hardie, Martin, English Coloured Books (1906, reprinted 1990) Gascoigne, Bamber, Milestones in Colour Printing 1457-1859 (Cambridge UP, 1997) Also various articles in the Journal of the Printing Historical Society - see: http://www.printinghistoricalsociety.org.uk/journal_indices/index.html Printing Chinese inventions English inventions History of printing Japanese inventions Printing Printmaking