Epson SQ-2550 User Manual page 126

Dot patterns
Your printer's print head is able to print graphics as well as text
because graphic images are formed on the printer about the
same
way that
printed. If you look closely at a newspaper photograph, you
can see that it is made up of many small dots. Your printer
also forms its images with patterns of dots, as many as 360 dot
positions per inch horizontally and 180 dots vertically. The
images printed by the printer can, therefore, be as finely
detailed as
the
Eight-element graphics
So that it is compatible with the
such printers such as the EPSON FX, RX, LX, and EX series, the
printer has an S-element graphics mode with six densities.
Although this mode uses only one third of the printer's nozzles,
it produces good quality graphics and allows you to use the
many programs written for 8-element graphics.
Twenty-four-element graphics
The graphics mode
print head is 24-element graphics. It has five densities, but for
simplicity this explanation will begin with only one of them,
triple-density.
Triple-density prints up to 180 dots per inch horizontally. As
the print head moves across the paper, every 1/180th of an inch
it must receive instructions about which of its 24 nozzles to fire.
At each position it can fire any number of nozzles from none to'
24. This means
information for each column it prints. Since
8-bit bytes of information in its communication with a
computer, it needs three bytes of information for each position.
pictures in newspapers and magazines are
ones at the beginning of this section.
takes full advantage of
that
the printer must receive 24 bits of
that
programs written for
many
the
Software and Graphics 4-11
Graphics
printer's
the
printer uses