Printronix LQH-HWTM manual Dark Printing, Command Codes

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.

	ADDED COLUMNS OF DOTS
NORMAL MODE	DARK MODE

Figure 3. Dark Printing

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