Product Features That Affect Print Quality; Proprietary Postscript Extensions; Device-Dependent Operators; Gray Shading-Setscreen And Setcolorscreen - Xerox DocuPrint 92C NPS Troubleshooting Manual

ADJUSTING PRINT QUALITY AND PERFORMANCE

Product features that affect print quality

Proprietary PostScript extensions

Device-dependent operators

Gray shading—setscreen and setcolorscreen
6-10
Note: If you are using a third-party finishing device connected
to DocuPrint by a bypass transport, the page delivery order is
determined by the requirements of the third-party device (face
up or face down). To maximize performance, place the pages in
the PostScript master in the order in which they are required by
the finishing device.
You can improve the appearance of your documents by being aware
of potential problems created through the use of proprietary
PostScript extensions and device-dependent operators.
PostScript masters that use proprietary printer features may cause
appearance inconsistencies between different PostScript printers.
Some PostScript printers contain proprietary PostScript extensions.
For example, some versions of the Apple Macintosh PostScript driver
download encrypted proprietary image "smoothing" operators to
Apple LaserWriters. The downloaded PostScript code uses the
product operator to determine if it is being used on a LaserWriter. If
not, the proprietary code is bypassed by doing a flushfile. This
allows the PostScript master to print on non–LaserWriter products.
As a result, PostScript masters generated on a Macintosh with Apple
proprietary features may produce output that varies between
LaserWriter and non–LaserWriter PostScript printers.
Some PostScript operators result in device-dependent PostScript
files. "Device dependence" means that devices having different
output characteristics may produce different-looking output even
though they use the same software. This section documents the
most serious examples of device dependence. The PostScript
Language Reference Manual, second edition, lists all of the graphics
state operators that are considered device-dependent.
The PostScript operators setscreen and setcolorscreen control the
PostScript halftone software that simulates various intensity levels of
gray and color inks. Because each PostScript product may have a
different default halftone definition, the halftone patterns and gray
scale range may differ also. Because setscreen is inherently device
dependent (especially when used for pattern fills), PostScript
masters look different on almost every different model of PostScript
printer.
The operators are also used to perform pattern fills, since PostScript
Level 1 does not have a pattern fill operator. (PostScript Level 2 has
pattern fill operators.) As stated in the PostScript Language
Reference Manual, first edition, "Remember that everything
pertaining to halftones is, by definition, device-dependent. In general,
XEROX DOCUPRINT 92C NPS TROUBLESHOOTING GUIDE