QMS 2425, Reference

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The ability of the printer to produce halftones allows you to add
scanned images or halftone graphics to your documents. This section
explains some of the options available on the QMS 2425/2425
TURBO for halftone printing.
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Continuous tone scanned images have to be converted to dot pattern
images on a laser printer. Laser printers, like printing presses, only
have the ability to print patterns of dots controlled by turning on and
off the laser. Because of the limited resolving power of the eye
halftones appear as continuous tone images. For example, if you hold
a newspaper photograph very close to your eyes, you can see the
halftone dots.
Halftone characteristics can be changed by settings available on your
QMS 2425/2425
TURBO Print System. The following factors can be
used to adjust the halftone characteristics of your documents:
„
Printer resolution
„
Screen frequency and screen angles (halftone types)
„
Smoothing
There can be some side effects to changing these factors. Factors
such as the number of gray levels, printer performance, and scanned
image quality can be affected.
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Gray levels are a progressive series of gray tones between black and
white. Gray levels are produced by varying the ratio of black to white
halftone dots. The number of gray levels depends on printer resolu-
tion and screen frequency.
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Screen frequency or lines per inch (lpi) is the number of lines of half-
tone dots that compose each inch of a halftone screen. The screen