Specifications
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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 will explain some of the options
available on the QMS 3260/4032 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 an example hold a
newspaper photograph very close to your eyes to see the halftone dots.
Halftone characteristics can be changed by settings available on your QMS 3260/
4032 Print System. The following factors can be used to adjust the halftone character-
istics of your documents.
Printer resolution
Screen frequency and screen angles (Halftone types)
There can be some side effects to changing these factors. Factors such as the num-
ber 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 lev-
els are produced by varying the ratio of black to white halftone dots. The number of
gray levels depends on printer resolution and screen frequency.
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Screen frequency or Lines Per Inch (LPI) is the number of lines of halftone dots that
compose each inch of a halftone screen. The screen frequency determines the num-
ber of halftone dots used to represent gray levels in a given area.
The following formula shows the relationship between screen frequency, print resolu-
tion and gray levels. As the screen frequency increases, the number of gray levels
decrease. If resolution is increased, the number of gray levels will also increase.
gray levels = (resolution/screen frequency)
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