tag:blogger.com,1999:blog-3407624264627208128.post6635999051516351288..comments2024-01-26T21:38:25.924-08:00Comments on Duane's PoeTree: Russ Cope writesDuanesPoeTreehttp://www.blogger.com/profile/17053093400086634552noreply@blogger.comBlogger1125tag:blogger.com,1999:blog-3407624264627208128.post-87815798869874010542016-06-17T03:23:16.620-07:002016-06-17T03:23:16.620-07:00Jakob Christoffel Le Blon was a painter and engrav...Jakob Christoffel Le Blon was a painter and engraver from Frankfurt who invented the system of three- and four-color printing in Amsterdam in 1710. He used the mezzotint method to engrave three or four metal plates (one per printing ink) to make prints with a wide range of colors. Based on his technique, televisions and computer monitors use RGB (red, green, and blue) to represent color images. This is an additive color model, since white is the "additive" combination of all primary colors. Similarly, because black is the absence of light, color printers and large presses employ the CMYK method that places dots of Cyan (blue), Magenta (red), Yellow, and Key (black) together.(The K for "key" is because the other plates are carefully keyed, or aligned, with the black one, which is often used as outline.) Colors are partially or entirely masked on a lighter background (usually white), which reduces the light that would otherwise be reflected. This method is called subtractive because the inks "subtract" brightness from white. Halftoning (also called screening) allows for less than full saturation of the primary colors; tiny dots of each primary color are printed in a pattern small enough that humans perceive a solid color. Magenta printed with a 20% halftone, for example, produces a pink color, because the eye perceives the tiny magenta dots on the large white paper as lighter and less saturated than the color of pure magenta ink. Without halftoning, the only available colors would be the three primaries plus three secondary colors produced by layering two of the primaries (cyan and yellow produce green, cyan and magenta produce blue, yellow and magenta produce red) and black (by layering all three of the primaries). Because RGB displays and CMYK prints employ such different technologies, the appearance of items on a monitor may not match the look of printed items if opposite color modes are being combined in both media. Since RGB and CMYK spaces are both device-dependent, there is no simple or general conversion formula between them. Conversions are generally via color management systems that use color profiles that describe the spaces being converted, but the conversions are not exact. A method of computing a colorimetric estimate of a color that results from printing various combinations of ink, in the case of halftone printing, treats each tiny overlap of color dots as one of 8 combinations of CMY or of 16 combinations of CMYK colors (Neugebauer primaries); however, the "dot gain" (the Yule–Nielsen effect) of scattered light complicates the physics and the analysis. In 1886, <br />Georges Seurat and Paul Signac developed a subtractive means of painting which art critics derided as "pointillism" -- small, distinct dots of color are applied in patterns to form an image. The style was in vogue for a while, in part because of the brighter nature of its imagery since it avoided the mixing of pigments and because some of the white canvas showed between the dots, but the resultant "Neo-Impressionism" it exemplified had a relatively short life. However, it reappeared in the 1960s in the form of Pop Art and Andy Warhol's early work.DuanesPoeTreehttps://www.blogger.com/profile/17053093400086634552noreply@blogger.com