Epson GT-30000 - Manual (Page 10)

Scanner Settings
6
The EPSON GT-30000 has several different built-in dither patterns as well as two user-definable,
downloadable dither patterns. Dither patterns are designed to apply a different threshold value to each pixel,
so as to avoid repetitive patterns (aliasing) in the scanned image. To determine the dither pattern that best
meets your needs, try each one on samples of your pages and use the one that gives the most pleasing
results. Generally you will use dithering when scanning photographs, but not when scanning text.
Note
Dithering usually increases the size of the compressed images, sometimes making
them bigger than their uncompressed counterparts.
Choose the desired dithering pattern from this drop-down list box. (If the box is dimmed, then dithering is
not available in the selected color mode.)
None No dithering. Recommended setting for scanning text and line art.
Dither Mode A 4 x 4 Bayer dither pattern
Dither Mode B 4 x 4 Spiral dither pattern
Dither Mode C 4 x 4 Net screen dither pattern
Dither Mode D 8 x 8 Net screen dither pattern
Download Pattern A
Download Pattern B
To download a dither pattern, click More to display the Advanced Settings
dialog box. Note: If you choose one of these pattern but no dither pattern
has been downloaded, the scanner will use the 4 x 4 Bayer pattern.
Dots per inch
Choose the desired scanning resolution from this drop-down list box. You can choose values between 50
and 2400 dpi. The higher the number of dots-per-inch, the larger will be the resulting image files. A 300 dpi
image has 90,000 dots per square inch; a 200 dpi image is less than half the size at 40,000 dots per square
inch. Scanning at 2400 dpi will produce huge files that contain almost six million dots per square inch. If
you use this resolution, you might run out of disk space (and time) before a normal-sized image has been
scanned. Normally you should choose the lowest resolution that gives the desired results and readability.
Brightness
Choose the desired brightness setting by using the Brightness controls. The EPSON GT-30000 has seven
levels of manual brightness control, as well as three preset levels: Normal, Darken, and Lighten. The three
preset levels are set in the scanner driver to provide somewhat consistent results on many different scanner
models, so the Normal setting is not always in the middle of the available range. This scanner does not have
an automatic brightness capability. To determine the best setting for your documents requires scanning,
changing the setting, then rescanning until you achieve the desired results.
In addition, when scanning in Black and White mode, you can adjust the Threshold setting in the
Advanced Settings dialog box (page 8). Because a binary image does not have a brightness associated with
it, pixels either being completely white or completely black, the Threshold control adjusts the gray level at
which the scanner switches a pixel from white to black. The scanner provides 256 Threshold settings.