Xerox 560, 550 manual PostScript, Overprint, Screening

100Chapter 11—Job parameters

Parameter	Option	Description
	PostScript	Uses the overprint information that exists in the PostScript
	overprint	file. This option also determines whether the DTP
		application's PostScript overprint settings are retained in
		the RIP.
Screening	Screening	Converts images, graphics and text into information that
		can be printed (halftone dots). The human eye “smoothes
		out” this information, which seems visually consistent with
		the original picture. Thus, the more lines per inch, the more
		natural the image appears. Screening is achieved by
		printing dots in numerous shapes or lines in an evenly
		spaced pattern. The distance between the screen dots or
		lines determines the quality of the image. Printers can work
		with constant amounts of toner and still produce a wide
		range of colors when you use screening. The darker the
		color, the larger the dot.
		To print an image on a digital printer or press, the color
		server needs to digitally approximate the grayscale values
		with different distributions of pixels. This process is
		commonly referred to as halftoning. Digital halftoning
		begins by sampling the original image at the same number
		of dots per inch as the printer and constructing digital
		halftone cells.