Canon CanoScan FB 630UI User Guide - Page 37

The Relationship Between the Gamma Curve and Image Brightness, Gamma = 1, Gamma < 1

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STEP 3 The Relationship Between the Gamma Curve and Image Brightness Gamma curve values fall with a range of 1 to 255. A gamma value of 1 appears as a straight line in the gamma graph, and if the value is any value other than one, the line on the gamma graph will appear curved. The relationship between the shape of the gamma curve and image brightness is explained below. Gamma = 1 Output Input and output and are equal and the gamma curve appears as a straight line, and the input image is displayed on the screen ª without adjustment. Gamma < 1 The data bends upward from the input shadow to highlight into the output area bending the curve up and making the adjusted image brighter in the display. Gamma > 1 The data bends downward from the input shadow to highlight away from the output area bending the curve down and making the adjusted image darker in the display. Output Output Input ª Input ª Input CAUTION • The gamma curve cannot be adjusted for a high definition color image that has been set with ColorSync because the tone adjustment is performed automatically. • The gamma curve cannot be adjusted for a Black & White (Line) image because mid-tones are shown as either black or white. To adjust the brightness of a Black & White image, use the threshold setting. (p. 48) 37

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37
S T E P
3
The Relationship Between the Gamma Curve and Image Brightness
Gamma curve values fall with a range of 1 to 255.
A gamma value of 1 appears as a
straight line in the gamma graph, and if the value is any value other than one, the line
on the gamma graph will appear curved.
The relationship between the shape of the
gamma curve and image brightness is explained below.
Gamma = 1
Input and output and are equal
and the gamma curve appears as
a straight line, and the input
image is displayed on the screen
without adjustment.
Gamma < 1
The data bends upward from the
input shadow to highlight into
the output area bending the curve
up and making the adjusted
image brighter in the display.
Gamma > 1
The data bends downward from
the input shadow to highlight
away from the output area
bending the curve down and
making the adjusted image darker
in the display.
CAUTION
• The gamma curve cannot be adjusted for a high definition color image that
has been set with ColorSync because the tone adjustment is performed
automatically.
• The gamma curve cannot be adjusted for a Black & White (Line) image
because mid-tones are shown as either black or white. To adjust the
brightness of a Black & White image, use the threshold setting.
(p. 48)
Output
Input
Output
Input
Output
Input