Ricoh B245-62 Service Training page 40

Overview
The machine automatically selects the most
appropriate ID gamma correction based on the
selected original type and the operation panel ID
setting.
In all modes, ID gamma correction can be
adjusted with SP 4923.
Gradation Processing
There are three types of gradation processing.
» Binary picture processing
» Error diffusion
» Dithering
(Continued in notes.)
Slide 40
Binary Picture Processing
The 8-bit image data is converted into 1-bit data (black and white image data). This is
done when the user selects Text 2 or Special 1. The threshold for deciding whether a pixel
is black or white cannot be adjusted.
Error Diffusion
Error diffusion reduces the difference in contrast between light and dark areas of a
halftone image. Each pixel is corrected using the difference between it and the surrounding
pixels. The corrected pixels are compared with an error diffusion matrix.
Error diffusion is applied when the user selects Text 1, Photo 1-3 and Special 2 and 5.
As the final step in error diffusion, a process called Texture Removal is applied to Text 1,
Photo 2, Special 2, and Special 5 by default, but can also be applied to Photo 1 and 3 by
changing the value of SP 4926.
Texture removal uses 256 threshold values in an 8 x 8 matrix. The value of SP 4926
controls the application of Texture Removal for each of the 6 modes listed above. The
settings are as follows:
0: The default value for each mode is used. Text 1, Photo 2, Special 2, and Special 5 have
a default of 3 (see below) and Photo 1 and 3 have a default of 1.
1: No removal applied.
2 – 6: Removal applied at the level specified here. The higher the setting (level), the less
clear the image will become (more texture removal).
Dithering
Each pixel is compared with the threshold in a dither matrix. Several matrices are available
to bring out half-tone areas in images such as newspaper-type photographs. Dithering is
only used for Special 3 and Special 4.
ID Gamma Correction
40
B245-62 / PD-C4