Specifications

Interpolation
In addition, many printers produce higher-resolution output by means of a process called
interpolation. Printer resolution is not just a physical matter of how small the dots created by a laser or
an inkjet can be; a higher-resolution image also means that the printer must process more data. A
1,200dpi printer must process 1,440,000 dots per square inch, whereas a 600dpi printer processes only
360,000 dots per square inch.
In this example, the higher-resolution image, therefore, requires four times the memory of its lower-
resolution counterpart and a great deal more processing and transfer time between the computer and
the printer. Some comparisons between printers would involve even greater differences in amounts of
data processed.
Interpolation uses algorithms to add pixels between the original pixel data; this is similar to the
process by which a scanner can produce scanned resolutions higher than its optical resolution sup-
ports. When used by printers, interpolation provides a smoother output because of the extra pixels
used in the image. Interpolation enables a printer designed to print at 600dpi to interpolate the image
to 1,200dpi, even though it lacks the required memory and processing power for true 1,200dpi out-
put.
Although an interpolated 1,200dpi image is better than a 600dpi image without interpolation, a
printer that operates at a true 1,200dpi resolution should produce noticeably better output than an
interpolated 1,200dpi. In addition, it will probably cost somewhat more as well. It is important when
you evaluate printers that you check to see whether the resolution specified by the manufacturer is
interpolated. Also, because interpolation techniques don’t always improve printouts, the user can nor-
mally disable this option in the printer’s properties sheet.
Paper Quality
Whereas laser printers produce their images by fusing toner to the paper, inkjet printers place the ink
on top of the paper. Although many general-purpose papers supposedly suitable for laser, copier, and
inkjet printers are sold, using anything less than true inkjet paper degrades the actual print resolution.
This is because inkjet paper should be smoother than laser/copier paper and promote rapid drying of
ink. Paper that lacks these features has loose fibers that cause the ink to “wick,” causing a fuzzy
appearance to inkjet printing. Photorealistic printing at resolutions above 720dpi usually requires the
use of photo-quality paper that is heavy, very smooth, and very fast drying. Many users’ disappoint-
ments with inkjet print quality stem from improper paper choices or from incorrect matching of
paper with printer modes. To make printing easier, most inkjet printers today allow the user to select
a single paper type at print time. This option then selects the correct combination of resolution and
printing techniques necessary for a top-quality print job.
Dot-Matrix Print Quality
Dot-matrix printers are different from inkjet and laser printers in several fundamental ways. Most
importantly, dot-matrix printers do not process an entire page’s worth of data at a time like lasers do
or a line of information like inkjet printers do; instead, they work with streams of characters. The
print resolution of a dot-matrix printer is based not on its memory or its processing power, but rather
on its mechanical capabilities. The grid of dots a dot-matrix printer uses to create characters is not a
data set in a memory array or a pattern on a photosensitive drum; the grid is formed by a set of metal
pins that physically strike the page in various combinations. The resolution of the printer is therefore
determined by the quantity of its pins, which usually number either 9 or 24. Because it uses more
pins to create characters of the same size, a 24-pin printer has pins that are necessarily smaller than
those of a 9-pin printer, and the dots they create are smaller as well. As with the other printer types,
smaller dots result in fewer jagged edges to the printed characters and a better appearance to the