Preparing gamma curve data, Example of prepared gamma curve data – Canon 800II User Manual
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Chapter 2 Specifying the Scanner Settings
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Preparing Gamma Curve Data
Gamma curve data consists of a 258-line text file (*.gmm) containing the output
values for the 256 levels of input values.
Always enter a connect as the first line of the gamma curve data and “256” in the
second line to indicate the number of data items.
Lines 3 onwards set the output values for each input value, starting with the output
values for “0” in line 3, “1” in line 4 and so on through to the output value for input
value “255” in line 258.
Smaller values in the gamma curve data give a darker image while larger values
produce a lighter image.
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Example of Prepared Gamma Curve Data
Normally, the gamma curve leans to the right. However, the leftward-leaning gamma
curve shown in the lower figure below inverts all the output values so that the result-
ing image is also inverted.
1st line
: inverted linear gamma curve
2nd line
: 256
3rd line
: 255
4th line
: 254
5th line
: 253
253rd line : 5
254th line : 4
255th line : 3
256th line : 2
257th line : 1
258th line : 0
Gamma curve data (inverted)
1st line
: gamma curve
2nd line
: 256
3rd line
: 0
4th line
: 1
5th line
: 2
253rd line : 250
254th line : 251
255th line : 252
256th line : 253
257th line : 254
258th line : 255
Gamma curve data
(Gamma curve)
Input value
Output value
(Gamma curve)
Output value
Input value