8.Features
© 2023 China Daheng Group, Inc. Beijing Image Vision Technology Branch 158
2)
How it works
The camera applies a Gamma correction value (
γ
) to the brightness value of each pixel according to the
following formula (red pixel value (R) of a color camera shown as an example):
R
corrected
=
(
R
uncorrected
R
max
)
γ
× R
max
The maximum pixel value (R
max
) equals, e.g., 255 for 8-bit pixel formats, 1023 for 10-bit pixel formats or
4095 for 12-bit pixel formats.
3)
Enabling Gamma correction
After enabling Gamma correction, set GammaValue to change the image brightness. The range of
GammaValue is 0 to 4.00.
a)
Gamma = 1.0: the overall brightness remains unchanged.
b)
Gamma < 1.0: the overall brightness increases.
c)
Gamma > 1.0: the overall brightness decreases.
In all cases, black pixels (gray value = 0) and white pixels (gray value = maximum) will not be adjusted.
If you enable Gamma correction and the pixel format is set to a 10-bit or 12-bit, some image
information will be lost. Pixel data output will still be 10-bit or 12-bit, but the pixel values will be
interpolated during the Gamma correction process, resulting in loss of accuracy and loss of image
information. If the Gamma feature is required and no image information is lost, avoid using the
Gamma feature in 10-bit or 12-bit pixel format.
4)
Additional parameters
Depending on your camera model, the following additional parameters are available:
a)
GammaEnable: Enable or disable Gamma correction.
b)
GammaMode: You can select one of the following Gamma correction modes:
User: The Gamma correction value can be set as expected.
sRGB: The camera's internal default Gamma correction value. This feature is used with the color
transformation feature to convert images from RGB to sRGB. It is recommended to adjust Gamma to
sRGB mode after enabling the color transformation feature.
8.4.5.
Lookup Table
When the analog signal that is read out by the sensor has been converted via ADC, generally, the raw
data bit depth is larger than 8 bits, there are 12 bits, 10 bits, etc. The feature of lookup table is to replace
some pixel values in the 8 bits, 10 bits, and 12 bits images by values defined by the user.
The lookup table can be a linear lookup table or a non-linear lookup table, created entirely by the user.