HP QMS 1660 - Manual (Page 105)

Gamma
Correction,
Halftones, and
Screens
5-5 Additional Technical Information
The following factors influence the quality of a halftone:
n
Printer resolution
n
Screen frequency of the halftone
n
Quality of the scan
n Diameter of the laser beam
Changing print resolution from 300x300 dpi to either 600x600 or
1200x600 dpi smooths the resulting spots. In addition, because each
spot is represented by a wider range of dots, a greater the number of
gray levels is possible. The laser beam is part of the print engine, so
it’s not a factor you can adjust.
» Note: The number of gray levels at 600x600 dpi and 1200x600 dpi is
the same. The enhanced print quality is due to elongated halftone
cells rather than to an increased number of gray levels.
Halftone Types
Your printer provides two different types of halftones—basic and
advanced. These two options allow you to customize the smoothness
of the printed image according to the number of grayscales it uses.
n
Basic— Regular dot placement at 53 lpi for 300x300 resolution or 71 dpi
for 600x600 resolution.
n
Advanced—Variable dot placement according to the grayscale
within the image. Generally, this option provides smoother transi-
tions between grayscales within the image.
» Note: When the advanced halftone type is chosen, gamma
correction has no effect on the image.
Screen Frequency
Screen frequency is the number of lines of dots that compose each
inch of a halftone screen. The screen frequency of a halftone deter-
mines the number of spots used to represent gray levels in a given
area. A 71 lines per inch (lpi) screen frequency has 71 lines of dots
for each inch of the halftone screen.