Specifications

As a result, the claims of WYSIWYG (what you see is what you get) output by software and hardware
manufacturers are valid only in the roughest sense. Even the lowest-resolution inkjet or laser printers
produce output that is far superior to that of your screen display:
■ Current SOHO-market laser printers have resolutions that range from 600dpi to 1200dpi.
■ Current SOHO-market inkjet printers have resolutions that range from 600dpi (black ink) to as
high as 720×2,880dpi or 2400dpi for full-color photo printing with special papers.
Increasing Print Resolution
It might seem that 90,000 dots per square inch is an extraordinary amount of detail, but at 300dpi,
printed characters can have noticeably jagged diagonal lines. Two ways to improve the quality of the
printed output and eliminate the “jaggies” exist. One way is to increase the resolution, as seen in the
previous printer comparisons. By itself, 600dpi or higher resolution is sufficient to eliminate the obvi-
ous jaggedness in the print output. This reduction in jaggedness is the first benefit of improving reso-
lution. Commercial offset printing (as used in the printing of this book, for example), by contrast,
usually runs from 1,200dpi to 2,400dpi; the difference between laser or inkjet printing and commer-
cial printing is still a large one, but not nearly as large as in the days of 300dpi or lower printers.
A second benefit of improved print resolution is the effect that higher resolutions have on photo-
graphic reproduction. Higher resolutions enable laser and inkjet printers in particular to create more
detailed and finer-grained photo printouts. The newest photorealistic inkjet printers combine high
resolutions with smaller ink droplets and special color printing techniques to create prints that rival
snapshot quality when viewed from a short distance.
600dpi and above laser printers also achieve better photographic reproduction, but through different
means. A true halftone, as seen in a newspaper photograph, uses dots of various sizes to reproduce
gray levels. Early-model laser printers were incapable of varying the size of dots, so they divided the
image to be printed into a grid and placed groups of pixels into each square of the grid (known as a
halftone cell) to simulate the different-size dots of a true halftone. This method is still used today, and
the higher resolution enables them to use smaller halftone cells to simulate halftoning, thus produc-
ing better quality photo printing.
As you’ll see later, high printer resolutions for inkjet printers are also heavily media dependent; you
can’t get the best print quality unless you use paper or other media made for high-resolution printing.
Resolution Enhancement
The quality of the print output can also be increased without increasing the resolution by varying the
size of the dots. This technique was originated by Hewlett-Packard and is called Resolution
Enhancement Technology (RET). RET uses smaller dots to fill in the jagged edges created by larger dots.
Because the dots are so small, the cumulative effect to the naked eye is a straight diagonal line. Other
manufacturers have developed their own versions of this concept by using other names, such as edge
enhancement. This type of enhancement is possible only for laser and inkjet printers. Because dot-
matrix printers produce images by having pins physically strike the page (through an inked ribbon),
they cannot use variable-size dots.
Inkjet printers use variable-size ink droplets during the dithering process, which produces colors—
such as orange—that must be mixed from the cyan, magenta, and yellow inks used by the printer.
The capability to mix colors and vary the size of droplets enables today’s best inkjet printers to come
incredibly close to photographic quality.