HP Color LaserJet 4650 series - Page 23

Evaluating color laser printers 19
Edge enhancements
The edge enhancements available with the HP Color LaserJet 4650 series printer provide precise
edge control, delivering excellent print quality. Edge control has three components: Color REt,
adaptive halftoning, and trapping. Color REt increases the apparent resolution by placing each dot
for the smoothest edges, adaptive halftoning increases the edge sharpness, and trapping reduces
the effect of color plane misregistration by slightly overlapping the edges of adjacent objects. These
features are designed into the printer through HP proprietary technologies and do not affect
printing speed.
ColorREt
Color REt is a new feature that smoothes edges by intelligently changing the size and position of
the dots that make up the edge of a solid object. It is optimized to work on solid color edges: red,
blue, green, black, and other solid colors. This ability to grow and move dots increases the
apparent resolution well above 600 dpi.
Adaptive halftoning
Adaptive halftoning increases the edge smoothness of text and graphics while maintaining the
quality of area fills. Adaptive halftoning provides a solution to the requirement for smooth color and
accurate, crisp edges by locating and increasing the digital halftone frequency at edges.
Trapping
To generate a color image, four color planes must be printed: cyan, magenta, yellow, and black.
Trapping is the deliberate overlapping of one color to an adjacent color to reduce the effect of
color plane misregistration.
Included in the trapping component is halo reduction. Halo reduction makes the subordinate colors
recede from the edge of the dominant color. For example, a process black line would be made up
of black, the dominant color, and cyan and magenta, the subordinate colors. The cyan and
magenta near the edge of the black line are reduced or removed. This prevents color from being
seen on the edge of the black line.
Color matching
The process of matching printer output color to your computer screen is quite complex because
printers and computer monitors use different methods of producing color. Monitors display colors
by light pixels using an RGB (red, green, blue) color process, but printers print colors using a
CMYK (cyan, magenta, yellow, and black) process.
Several factors can influence your ability to match printed colors to those on your monitor. These
factors include:
• Print media
• Printer colorants (inks or toners, for example)
• Printing process (inkjet, press, or laser technology, for example)
• Overhead lighting
• Personal differences in perception of color
• Software applications
• Print drivers
• PC operating system
• Monitors
• Video cards and drivers
• Operating environment (humidity, for example)
Keep the above factors in mind when colors on your screen do not perfectly match your printed
colors. For most users, the best method for matching colors on your screen to your printer is to print
sRGB colors.