Specifications

Use the printer selection criteria section later in this chapter to help you focus on the most important
features you need.
Color Laser Printers
Color laser printers are a relatively recent development when compared to the other technologies dis-
cussed here. The technology is the same as that of a monochrome laser printer, except that it has four
toners in different colors. Unlike the other types of color printers, which apply all the colors at the
same time, many color lasers actually print each color on the page individually. Because the printer
has only a single photoreceptor drum, the entire print engine cycle repeats four times for each page,
applying the colored toners on top of each other.
This method greatly complicates the printer’s paper handling. In a monochrome printer, the page
passes beneath the photoreceptor drum at a speed equal to the drum’s rotation so the toner can be
applied evenly onto the page. In a color printer, however, the page must reverse so that it can pass
under the drum four times. In addition, the page must be in precisely the same position for each pass
(registration) so the individual dots of different colors fall directly on top of one another.
Toner levels can affect the quality of output from laser printers. Just as with monochrome lasers or
copiers, a gradual degradation of quality occurs—or variations in print density—over the life of a
toner cartridge. This becomes most noticeable as the toner runs out and is compounded in a color
laser by the fact that four toner cartridges are used.
Color lasers can suffer from registration problems due to the fact that the same piece of paper has to
make four passes. If any misalignment occurs, the colors will be slightly smeared or smudged.
Textured paper types also can pose problems. If the paper has a textured or rough surface, such as
classic laid bond, toner is deposited in both the high and low spots, but the fuser rollers might not
exert sufficient pressure to reach the depressions. As a result, the toner can remain a powder in those
places and can be brushed off during normal handling.
To overcome the speed and registration problems of conventional color laser printers, the LED page
printer mechanism (using light-emitting diodes instead of a laser) pioneered in desktop printers by
Okidata is now being used by both Okidata and Lexmark in some color page-printer models. Printers
using LEDs can print color pages at the same speed as monochrome pages because they can place all
four colors in a single pass. Some lasers mix the toner on the drum by applying each toner in turn,
after which all four colors are laid onto the paper at once. This eases the paper-handling difficulties
but presents other problems when applying the toner to the drum. In either case, the result is four
toner colors mixed on the page and passing through the fuser assembly at once. This technique pro-
vides results that are vastly superior to dithered inks and other media. However, color laser printers
are still very expensive, with PostScript-compatible models starting at $2,000–$3,000. Also, because
the drum must rotate four times for each page, these printers are significantly slower than mono-
chrome lasers. Although new developments in host-based color laser printers designed for Windows
9x and NT have dropped the price of some models below $1,300, host-based printers generally are
unsuitable for elaborate graphics printing.
In addition to the relatively high initial costs of color laser printers, the type and costs of consum-
ables and accessories should also be considered before acquiring a color laser printer.
Environmental Issues with Color Laser Printers
Humid or dry conditions can affect laser output as well. As the paper passes through the laser printer,
it receives a static charge so the oppositely charged toner can adhere to it. If the static charge on the
paper is too great due to low humidity, the toner can spread or splatter when transferred to the paper.
On the other hand, if the humidity is high and the paper won’t hold a charge, the toner might not
transfer to the page effectively, resulting in uneven print.