Printronix LQH-HWTM - Manual (Page 28)

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Chapter 2 Command Codes
Dark Printing
A DARK parameter, available in the Alpha, Reverse, and Bar Code
commands, is a double-strike feature which produces bolder, darker text,
denser black backgrounds for reverse print, and extra-dark, more readable
bar codes.
A DARK parameter used with alphanumeric text in the ALPHA command will
print using a bold font.
The extra darkness provided by the DARK parameter improves the Print
Contrast Ratio (PCR) and effectively extends the life of the ribbon. For bar
codes, the PCR describes the difference in light reflection between the bars
and spaces as a measurement of light/dark contrast in order to judge when a
printed bar code will not be dark enough to be read with accuracy by a
scanner. The extra dots used to produce the darker bar code do not change
the overall width of the wide bars. Figure 3 illustrates how the DARK
parameter adds two extra dot columns to wide bar code bars without
increasing bar width.
Due to the second hammer bank stroke required to plot the extra columns of
dots, print speed may be reduced up to half when the DARK parameter is
used with Bar Code commands. However, this decreased print speed should
be weighed against the significant increase in bar code PCR and extended
ribbon life.
Figure 3. Dark Printing
NORMAL MODE
ADDED COLUMNS OF DOTS
DARK MODE