Adobe Illustrator CS3 - Manual (Page 409)

ILLUSTRATOR CS3
User Guide
403
The PPD files for high-resolution imagesetters offer a wide range of possible line-screen rulings paired with various
imagesetter resolutions. The PPD files for lower-resolution printers typically have only a few choices for line screens,
and they are coarser screens of between 53 lpi and
85 lpi. The coarser screens, however, give optimum results on
lower-resolution printers. Using a finer screen of 100 lpi, for example, actually decreases the quality of your image
when a low-resolution printer is used for final output. That’s because increasing the lpi for a given resolution
decreases the number of colors that can be reproduced.
Note: Some imagesetters and desktop laser printers use screening technologies other than halftoning. If you are printing
an image on a nonhalftone printer, consult your service provider or your printer documentation for the recommended
resolutions.
Change the printer resolution and screen frequency
Adobe Illustrator prints fastest and best by using the default printer resolution and screen frequency. However, in
some cases, you might want to change the printer resolution and screen frequency—for example, if you draw a very
long curved path that won’t print due to a limit-check error, if printing is slow, or if gradients and meshes show
banding when printed.
1 Choose File > Print.
2 For Printer, select a PostScript printer, Adobe PostScript® File, or Adobe PDF.
3 Select Output on the left side of the Print dialog box.
4 For Printer Resolution, select a screen frequency (lpi) and printer resolution (dpi) combination.
Printing color separations
About color separations
To reproduce color and continuous-tone images, printers usually separate artwork into four plates (called process
colors)—one plate for each of the cyan, magenta, yellow, and black portions of the image. You can also include custom
inks (called spot colors). In this case, a separate plate is created for each spot color. When inked with the appropriate
color and printed in register with one another, these colors combine to reproduce the original artwork.
The process of dividing the image into two or more colors is called color separating, and the film from which the
plates are created are called the separations.
Composite image printed on a color laser printer compared to four-color separations printed on an imagesetter.
To produce high-quality separations, you should work closely with the print shop that will produce your separations,
consulting its experts before beginning each job and during the process.