Gamma Correction; Correction For Color Reproduction On A Display - Basler acA2040-55 User Manual

Features

7.13 Gamma Correction

The gamma correction feature lets you modify the brightness of the pixel values output by the
camera's sensor. The correction is useful to account for non-linearity in the human perception of
brightness.
For color cameras, gamma correction is always performed in the RGB color space regardless of
the selected pixel format.
To accomplish gamma correction, a gamma correction value (γ) is applied to the pixel value of each
pixel according to the following formula (shown for the red pixel value (R) of a color camera as an
example):
The formula uses uncorrected and corrected pixel brightnesses that are normalized by the
maximum pixel brightness. The maximum pixel brightness equals 255 for 8 bit output, 1023 for
10 bit output, and 4095 for 12 bit output.
The Gamma correction value can be set in a range from 0 to 3.99998.
When the Gamma correction value is set to 1, the output pixel brightness is not corrected. The
gamma correction value of 1 is the default value after camera reset or power up.
A Gamma correction value between 0 and 1 results in increased overall brightness, and a gamma
correction value greater than 1 results in decreased overall brightness.
In all cases, black and white are not corrected (black: output pixel brightness equals 0; white: output
pixel brightness equals 255 for 8 bit output, 1023 for 10 bit output, and 4095 for 12 bit output).

7.13.1 Correction for Color Reproduction on a Display

Most displays are designed to represent colors in sRGB color space. Accordingly, colors provided
by the camera must undergo an sRGB gamma correction for correct color reproduction on a display.
If you do not use a light source preset (by selecting "Off" as the light source preset): Apply a

Gamma parameter value of approximately 0.45. This is equivalent to applying an sRGB
gamma correction.
If you use a light source preset (Daylight 5000 K, Daylight 6500 K or Tungsten 2800 K) the

necessary sRGB gamma correction is automatically applied. Make sure the Gamma
parameter value is set to 1. In this way you are, in effect, not applying any gamma correction
by means of the Gamma parameter and the automatic sRGB gamma correction can operate
undisturbed. If you nonetheless used a Gamma parameter value other than 1 it would be
combined with the automatically set sRGB gamma correction value, causing incorrect colors.
For more information about light source presets, see Section 7.14.3.3 on
270
R

uncorrected
-------------------------- -
R =

corrected
R
max
γ

×
R

max
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Basler ace USB 3.0