QMS 4060 Technical Information download pdf (Page 147)

Halftones

5-5

Additional Technical Information

Screen Frequency

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 number of halftone dots used to

represent gray levels in a given area.

The following formula shows the relationship between screen fre-

quency, print resolution 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.

n gray levels = (resolution/screen frequency)

+ 1

You can change screen frequency by selecting the halftone type in

the QMS 4060 configuration menu, through your application, or by

using the PostScript setscreen operator.

The extra gray levels available through higher resolution provide a

smoother shift from the darkest black to very light grays.

Screen Angle

A screen angle is the angle at which a halftone screen prints. The

default screen angle for your QMS 4060 Print System is 45° at

300x300, and 600x600. This is the normal angle for black and white

printers. Selecting advanced halftone types menu option will vary the

screen angle. You can also change the screen angle through the

PostScript setscreen operator.

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QMS 4060 Technical Information Page 147