A75UM3EA (Ver. E.2)
3-58
B. Function of Threshold Level in the Line/Photo Mode
Letters (Black)
Foggy background
Letters (Gray)
(Like a newspaper)
Dirt
Solid black
Halftones
Black dots (Dirt)
Solid Black
Lines (Gray) Line image
The purpose to change the Threshold Level in the Line/Photo Mode is to remove unnecessary light
images from the copy similar to the case of the Line Mode.
When some original is scanned, densities of all its images are detected and compared with the
selected Threshold Level in order to divide images into 2 groups such as βnecessary dark imageβ and
βunnecessary light imageβ.
Since βunnecessary light imageβ is converted to βwhite imageβ, the copy will not have such image.
Whenever you select larger Threshold Level, the scanner tends to judge light image to be
βnecessary dark imageβ.
Whenever you select smaller Threshold Level, on the contrary, it tends to judge light image to
be βunnecessary light imageβ.
1. If the selected Threshold Level is large, it becomes impossible or difficult to read the copy since
such unnecessary light images as βFoggy backgroundβ, βDirtβ and βBlack dotsβ are judged
βnecessary dark imageβ and the copy has these images as the following examples 1 and 2.
(Example 1 : Threshold Level is too large.)
(Original) (Result of copy)
(Example 2 : Threshold Level is a little large.)
(Original) (Result of copy)
ABCDE
12345
ξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξ
ξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξ
ξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξ
ξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξ
ξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξ
ξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξξ
To Next Page
Loading...
