Characteristic Detection; Filtering; Overview; Mtf Filter - Ricoh Russian-C2a Service Manual

10 August, 2001

Characteristic Detection

This function uses software filters to detect edge areas, non-edge areas, and areas
of shaded dot patterns.
The result determines the image processing that will be applied to each pixel.

Filtering

Overview

There are some software filters for enhancing the desired image qualities of the
selected original mode. These filters are the MTF filter, the smoothing filter,
characteristic filter, and independent dot erase.
Depending on the original mode and the reproduction ratio, the machine will use
either MTF/smoothing, or the filter determined by characteristic detection.
If MTF/smoothing is used, it is applied to all areas of the original, regardless of
whether they are edge areas, non-edge areas, or independent dots.
• The MTF filter emphasizes sharpness and is used in all original types except
Photo mode.
• The smoothing filter is used in Photo mode.
If the characteristic filter is used, the filter for each pixel depends on the image data
type that was detected by characteristic detection.

MTF Filter

An MTF filter is used for all original types except Photo mode.
When the reproduction ratio is less than 35%, this filter is applied to all image data
pixels, regardless of whether they are in an edge area or non-edge area.
When the reproduction ratio is 35% or more, the type of MTF filter used for each
pixel depends on the results of characteristic detection.

Smoothing Filter

A smoothing filter is used in Photo mode instead of MTF. It is applied to all image
data pixels, regardless of whether they are in an edge area or non-edge area.
With some combinations of reproduction ratio and image mode, the type of
smoothing used for each pixel depends on the results of characteristic detection
(see the Photo mode table in SP Modes for Each Processing Step).

Characteristic Filter

A characteristic filter is applied instead of MTF, smoothing, and ID gamma
correction with some combinations of original type and reproduction ratio. See the
'SP Modes for Each Processing Step' section.
For example, In text mode, for the 'Normal' original type, if the reproduction ratio is
less than 35%, MTF (medium) is used for all pixels in the image. However, if the
reproduction ratio is 35% or more, the 'medium' characteristic filter is used, and the
processing depends on whether the pixel was in an edge area, a non-edge area, or
in an area shaded using a dot pattern.
2-17
IMAGE PROCESSING