Dalsa Linea2 5GigE, Руководство пользователя

Страница: 87 / 164

80 • Operational Reference Linea2 5GigE Series Camera
LUT Size vs. Output Pixel Format
The LUT size will be the same as the sensor pixel size. All camera processing is performed at the
sensor pixel format of the camera, while the user chooses the output pixel format (such as 8-bit).
Using the example of a 12-bit camera, the LUT table is also 12-bit. The Linea2 default neutral LUT
programming is as follows:
• When the Output Pixel format = 12-bit , the default LUT data value is equal to the LUT index
value for each index. This is a linear LUT that does not modify the sensor data.
• When the Output Pixel format = 8-bit , the default LUT data is programmed to map the 4096
sensor pixel values to 256 output values. Therefore, LUT indices “0 to 15 ” have value “0”, LUT
indices “ 16 to 31 ” have value “1”, and so on.
LUT data is selected either as a predefined gamma correction, or is programmed with individual
values for various LUT index entries; a user LUT data file may be uploaded using the File Access
control. Refer to the Sapera documentation for information about the SapLut Class. Note that a
SapLut file can be uploaded to the device but cannot be read back.
Gamma Correction Factor
The following graphic shows LUT output data as a function of the gamma correction factor
programmed by the user. An 8-bit LUT is shown as an example. Note that the graphic is not to
scale.
• As Gamma Correction is reduced in value to the minimum allowed, the nonlinear output of
acquisition data through the LUT effectively boosts low value data.
• As Gamma Correction is increased in value to the maximum allowed, the nonlinear output of
acquisition data through the LUT effectively reduces low value data.
DN=00
DN=255
LU
T
O
u
tp
u
t
Input DN
DN=00
DN=255
Gamma Factor going to min.
Gamma Factor going to max.
Figure 58: Depiction of a gamma function.