Epson ES-800C, User Manual

Page: 72 / 89

Halftoning mode
Halftoning is a process of changing an image to a pattern of
dots. This is required because a printing press produces images
in a different way than photography does.
Photographs have an almost infinite number of tones, with an
almost infinite number of colors for color photographs, but
printing uses only individual single-color dots. Black and white
images use black dots, and color images use only four colors of
dots: cyan (blue), magenta (red), yellow, and black. The size
and spacing of these dots is varied to simulate photographic
continuous tones. In some halftoning the dots are quite
noticeable, as you can see in the illustration on page 3-8 of this
manual. If the dots are fine enough, however, the printed image
appears to have continuous tones, as you can see on pages 16
and 18 of the Color Image Scanner booklet.
You can choose various types of halftoning at the time you
scan, but it is nearly always best to choose halftoning of “off” or
“none” and have the halftoning done by the image editing
software or by the output device (such as a laser printer). The
illustration on page 3-8 was scanned in gray scale with no
halftoning and printed on a black and white laser printer. The
printer performed the halftoning so that it could print the
image. You can see the dots in the illustration.
You will always get better results scanning from a photograph
than from a printed image, such as a picture in a newspaper or
magazine, because printed images have already been halftoned
and you may see a conflict in the halftone methods. Therefore,
you should not scan the color images in the Color Image Scanner
booklet; use black and white or color photographs for better
test results.
Appendix A-9