Specifications

Figure 8 Color laser and LED printers transfer the ink (left) to a photoconductor surface (top center)

before it can be transferred to paper. Because four colors are used, this process requires four passes to print a

single page with laser printers, but LED printers can print all four colors with a single pass. Color inkjet

printers spray the colored inks directly onto the paper surface (bottom center), printing all colors in a single

pass. In either case, the printer must control the placement of primary colors to accurately reproduce the

original document.

In most cases, dithering is only a moderately successful color process. The resolution of some color

printers is not high enough to prevent you from seeing the individually colored dots if you look care-

fully. The cumulative effect is of a solid color when seen from a distance, but close up, the dithering

pattern can be discernible to the naked eye. Some methods of overcoming these limitations include

HP’s use of color layering, Canon’s use of variable-sized ink droplets (similar to laser printer “font

smoothing” technologies), Xerox/Tektronix’s use of solid ink with superfine pitch, many vendors’ use

of six ink colors instead of just four for photo printers (increasing print resolution into the 1,000dpi

or higher range), and the development of photo-optimized high-gloss paper. These technologies are

found on most mid-range ($150 and up) inkjet printers and can produce stunningly good results.

Printing in color necessarily complicates the language the printer uses to communicate with the PC.

Only the PostScript page description language has supported color from its inception. A version of

PCL 5 with extensions to accommodate color, called PCL 5c, was introduced by Hewlett-Packard in

1994 and is still used by HP on its color LaserJet printers. Most inkjet printer manufacturers, however,

have their own proprietary color printing technologies, usually employing the printer driver to per-

form the additional processing required within the PC.

Obviously, many applications are available for color printing, but the true test of any color printer is

photographic reproduction. Dithered color that is acceptable for use in a bar chart, for example,

might be totally inappropriate for printing photographs. Although the first high-resolution color

inkjet and laser printers produced decent-looking photos only when the output was viewed from a

distance, color inkjet printers in the $250 and up range are now capable of honestly claiming

near–continuous-tone photo quality because of the technical developments mentioned in earlier

sections.

Need even better quality? If you are looking strictly for snapshot printing, consider the low-cost ($300

and up) dye-sublimation printers available from many of the same vendors that produce digital cam-

eras and DV camcorders.

If you’re a graphic artist who needs high-quality proofing, consider large-format inkjet, laser, LED, or

solid-ink printers that provide full-color output at 800dpi or above and have PostScript RIPs included.

The leader in print quality by many accounts continues to be the Xerox/Tektronix solid-ink-

technology printers (originally developed by Tektronix and now sold by Xerox).

Drum

Yellow

Magenta

Cyan

Black

then

Photoconductor

Intermediate

transfer surface

Direct to paper

To paper