Cheetah Python Camera with USB3 Interface
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User Manual
December 5, 2017
Page
72
of
78
Rev 1.0
When Auto-White Balance (AWB) Tracking mode is selected, you can select five tracking
speeds from slow to fastest.
5.13 Transfer Function Correction
The user-defined LUT (Lookup Table) feature allows you to modify and transform the
original video data into any arbitrary value. The LUT enables transforming any 12-bit value
into any other 12-bit value. For the 10-bit Python sensor, the camera multiplies the 10-bit
pixel data by 4 to get 12-bit pixel data for input to the 12-bit LUT. After the 12-bit LUT
transforms the data, the camera divides the 12-bit data by 4 to get 10-bit pixel values for
output to the camera interface (refer to the following figure). The camera supports two
separate lookup tables, each consisting of 4096 entries, with each entry being 12 bits
wide. The first LUT is factory programmed with a standard Gamma 0.45. The second LUT
is not pre-
programmed in the factory. Both LUT’s are available for modifications, and
you
can generate and upload a custom LUT using the Imperx Upload Utility application.
Figure 44: Look up table.
5.13.1 Standard Gamma Correction
The image generated by the camera is normally viewed on a monitor and does not have a
linear transfer function, that is, the display brightness is not linearly proportional to the
scene brightness (as captured by the camera). The camera has a built-in transfer function
to compensate for this non-linearity called gamma correction. Gamma correction can also
help map the camera’s wider dynamic range to the limited dynamic range of the display.
If enabled, the video signal is transformed by a non-linear function close to the square
root function (0.45 power) as shown the following formula:
Formula: Output signal [V] = (input signal [V])
0.45
Figure 45: Gamma corrected video signal.
