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Understanding Printing Terminology
I’m not a big believer in glossaries. Generally, they contain glib, jargony, out-of- context definitions — about as helpful in gaining understanding of a concept as a seminar in which all the presenters speak pig latin. But before I delve into the inner recesses of printing, I want to introduce, in a semilogical, sort of random order, a smattering of the printing terms you’ll encounter. Ood-gay uck-lay.
Service bureau: A service bureau is a shop filled with earnest, young graphic artists (at least they were young and earnest when I worked at one), printer operators, and about a billion dollars’ worth of hardware. A small service bureau is usually outfitted with a few laser printers, photocopiers, and self- service computers. Big service bureaus offer scanners, imagesetters, film recorders, and other varieties of professional-quality input and output equipment.Service bureaus once relied exclusively on the Macintosh. This has changed, but a substantial number of Mac-based service bureaus remain. Most service bureaus are equally ready to help Photoshoppers on both PC and Mac platforms, but many will take your Windows Photoshop file and run it through a Mac. Nothing is wrong with this — Photoshop is nearly identical on the two platforms — but cross-platform problems may crop up. If you’re a PC user, try to be sure your service bureau knows how to address cross-platform incompatibilities and has a general working knowledge of Windows.
Commercial printer: Generally speaking, a commercial printer takes up where the service bureau leaves off. Commercial printers reproduce black-and-white and color pages using offset presses, web presses, and a whole bunch of other age-old technology I don’t cover in this miniglossary (or anywhere else in this book, for that matter). The process is less expensive than photocopying when you’re dealing with large quantities, say, more than 100 copies, and it delivers professional-quality reproductions.
Output device: This is just another way to say printer. Rather than writing Print your image from the printer, which sounds repetitive and a trifle obvious, I write Print your image from the output device. Output devices also include laser printers, imagesetters, film recorders, and a whole bunch of other machines.
Laser printer: A laser printer works much like a photocopier. First, it applies an electric charge to a cylinder, called a drum, inside the printer. The charged areas, which correspond to the black portions of the image being printed, attract fine, petroleum-based dust particles called toner. The drum transfers the toner to the page, and a heating mechanism fixes the toner in place. Most laser printers have resolutions of at least 300 dots (or printer pixels) per inch. The newer printers offer higher resolutions, such as 600 and 1,200 dots per inch (dpi).
Color printers: Color printers fall into three categories. Generally speaking, inkjet and thermal-wax printers are at the low end, and dye-sublimation printers occupy the high end. Inkjet printers deliver colored dots from disposable ink cartridges. Thermal-wax printers, which aren’t much in vogue these days, apply wax-based pigments to a page in multiple passes. Both kinds of printers mix cyan, magenta, yellow, and, depending on the specific printer, black dots to produce full-color output. Inkjet output quality can be quite good, but if you want truly photographic quality prints, you must migrate up the price ladder to dye-sublimation printers. Dye-sub inks permeate the surface of the paper, literally dying it different colors. Furthermore, the cyan, magenta, yellow, and black pigments mix in varying opacities from one dot to the next, resulting in a continuous-tone image that appears nearly as smooth on the page as it does on screen.
Imagesetter: A typesetter equipped with a graphics page-description language (most often PostScript) is called an imagesetter. Unlike a laser printer, an image- setter prints photosensitive paper or film by exposing the portions of the paper or film that correspond to the black areas of the image. The process is like exposing film with a camera, but an imagesetter knows only two colors: black and white. The exposed paper or film collects in a lightproof canister. In a separate step, the printer operator develops the film in a processor. Developed paper looks like a typical glossy black-and-white page. Developed film is black where the image is white and transparent where the image is black. Imagesetters typically offer resolutions between 1,200 and 3,600 dpi. But the real beauty of imageset pages is that blacks are absolutely black (or transparent), as opposed to the irregular gray you get with many laser-printed pages.
Film recorder: A film recorder transfers images to full-color 35mm and 45 slides, perfect for professional presentations. Slides also can be useful to provide images to publications and commercial printers. Many publications can scan from slides, and commercial printers can use slides to create color separations. So, if you’re nervous that a color separation printed from Photoshop won’t turn out well, ask your service bureau to output the image to a 35mm slide. Then have your commercial printer reproduce the image from the slide.
PostScript: The PostScript page-description language was the first product developed by Adobe — the same folks who sell Photoshop — and is now a staple of hundreds of brands of laser printers, imagesetters, and film recorders. A page-description language is a programming language for defining text and graphics on a page. PostScript specifies the locations of points, draws line segments between them, and fills in areas with solid blacks or halftone cells (dot patterns that simulate grays). Some newer printers instead use stochastic screens that simulate grays and colors using almost-random patterns.
Spooling: Printer spooling allows you to work on an image while another image prints. Rather than communicating directly with the output device, Photoshop describes the image to the system software. Under Windows 2000, you set spooling options using the Printer control panel. Choose SettingsPrinters, right-click the icon for your specific printer, and choose Properties from the pop-up menu. In the printer’s Properties dialog box, switch to the Details panel and click the Spool Settings button. Under Windows XP, the spooling settings are in the Advanced panel of the Properties dialog box. When Photoshop finishes describing the image — a relatively quick process — you are free to resume working while the system software prints the image in the background. This isn’t an issue anymore under Mac OS X, which has spooling turned on at all times.
Calibration: Traditionally, calibrating a system means synchronizing the machinery. In the context of Photoshop, however, calibrating means to adjust or compensate for the color displays of the scanner, monitor, and printer so what you scan is what you see on screen, which in turn is what you get from the printer. Colors match from one device to the next. Empirically speaking, this is impossible; a yellow image in a photograph won’t look exactly like the on-screen yellow or the yellow printed from a set of color separations. But calibrating is designed to make the images look as much alike as possible, taking into account the fundamental differences in hardware technology. Expensive hardware calibration solutions seek to change the configuration of scanner, monitor, and printer. Less expensive software solutions, including those provided by Photoshop, manipulate the image to account for the differences between devices.
Brightness values and shades: As described in Chapter 4, there’s a fundamental difference between the way your screen and printer create gray values and colors. Your monitor shows colors by lightening an otherwise black screen; the printed page shows colors by darkening an otherwise white piece of paper. On-screen colors, therefore, are measured in terms of brightness values. High values equate to light colors; low values equate to dark colors. On the printed page, colors are measured in percentage values called shades or, if you prefer, tints. High-percentage values result in dark colors, and low-percentage values result in light colors.
Composite: A composite is a page that shows an image in its entirety. A black- and-white composite printed from a standard laser printer or imagesetter translates all colors in an image to gray values. A color composite printed from a color printer or film recorder shows the colors as they actually appear. Composites are useful any time you want to proof an image or print a final grayscale image from an imagesetter, an overhead projection from a color printer, or a full-color image from a film recorder.
Proofing: To proof an image is to see how it looks on paper before the final printing. Consumer proofing devices include laser printers and color inkjet printers, which provide quality and resolution sufficient only to vaguely predict the appearance of your final output. Professional-level proofing devices include the Rainbow dye-sublimation printer and Matchprint laser proofer, both developed by Imation, DuPont’s toner-based Cromalin, and Creo’s Iris, the latter of which uses a special variety of inkjet technology.
Bleeds: Simply put, a bleed is an area that can be printed outside the perimeter of a page. You use a bleed to reproduce an image all the way to the edge of a page, as in a slick magazine ad. For example, this book includes bleeds. Most of the pages — such as the page you’re reading — are encircled by a uniform 2- pica margin of white space. This margin keeps the text and figures from spilling off into oblivion. A few pages, however — including the parts pages and the color plates — print all the way to the edges. In fact, the original artwork goes 2 picas beyond the edges of the paper. This ensures that if the paper shifts when printing — as it invariably does — you won’t see any thin white edges around the artwork. This 2 picas of extra artwork is the bleed. In Photoshop, you create a bleed by clicking the Bleed button in the Print with Preview dialog box.
Color separations: To output color reproductions, commercial printers require color separations (or slides, which they can convert to color separations for a fee). A color-separated image comprises four printouts, one each for the cyan, magenta, yellow, and black primary printing colors. The commercial printer transfers each printout to a plate, which is used in the actual reproduction process.
Duotone: An 8-bit grayscale image in Photoshop can contain as many as 256 brightness values, from white on up to black. A 16-bit grayscale image can contain thousands of brightness levels. Most printers can convey significantly fewer shades. A laser printer, for example, provides anywhere from 26 to 65 shades. An imagesetter provides from 150 to 200 shades, depending on resolution and screen frequency. And this assumes perfect printing conditions. You can count on at least 30 percent of those shades to get lost in the reproduction process. A duotone helps to retain the depth and clarity of detail in a grayscale image by printing with two inks. The number of shades available to you suddenly jumps from 150 to a few thousand. Photoshop also lets you create tritones (three inks) and quadtones (four inks). Note that using more inks translates to higher printing costs.
Spot color: Most color images are printed as a combination of four process color inks — cyan, magenta, yellow, and black. But Photoshop also lets you add premixed inks called spot colors. As I mentioned in Chapter 4, the most popular purveyor of spot colors in the United States is Pantone, which provides a library with hundreds of mixings. But many large corporations use custom spot colors for logos and other proprietary emblems. Most spot colors fall outside the CMYK gamut and thus increase the number of colors available to you. In addition to using spot colors in duotones, Photoshop lets you add a spot color channel to any image.
