Luminance Lookup Table - Basler Pioneer User Manual

Standard Features

13.7 Luminance Lookup Table

The camera can capture pixel values at a 12 bit depth. When a monochrome camera is set for the
Mono 16 or Mono 12 packed pixel format, the camera outputs 12 effective bits. Normally, the 12
effective bits directly represent the 12 bit output from the camera's ADC. The luminance lookup
table feature lets you use a custom 12 bit to 12 bit lookup table to map the 12 bit output from the
ADC to 12 bit values of your choice.
The lookup table is essentially just a list of 4096 values, however, not every value is the table is
actually used. If we number the values in the table from 0 through 4095, the table works like this:
The number at location 0 in the table represents the 12 bit value that will be transmitted out of
the camera when the sensor reports that a pixel has a value of 0.
The numbers at locations 1 through 7 are not used.
The number at location 8 in the table represents the 12 bit value that will be transmitted out of
the camera when the sensor reports that a pixel has a value of 8.
The numbers at locations 9 through 15 are not used.
The number at location 16 in the table represents the 12 bit value that will be transmitted out of
the camera when the sensor reports that a pixel has a value of 16.
The numbers at locations 17 through 23 are not used.
The number at location 24 in the table represents the 12 bit value that will be transmitted out of
the camera when the sensor reports that a pixel has a value of 24.
And so on.
As you can see, the table does not include a defined 12 bit output value for every pixel value that
the sensor can report. So what does the camera do when the sensor reports a pixel value that is
between two values that have a defined 12 bit output? In this case, the camera performs a straight
line interpolation to determine the value that it should transmit. For example, assume that the
sensor reports a pixel value of 12. In this case, the camera would perform a straight line
interpolation between the values at location 8 and location 16 in the table. The result of the
interpolation would be reported out of the camera as the 12 bit output.
Another thing to keep in mind about the table is that location 4088 is the last location that will have
a defined 12 bit value associated with it. (Locations 4089 through 4095 are not used.) If the sensor
reports a value above 4088, the camera will not be able to perform an interpolation. In cases where
the sensor reports a value above 4088, the camera simply transmits the 12 bit value from location
4088 in the table.
The advantage of the luminance lookup table feature is that it allows a user to customize the
response curve of the camera. The graphs below represent the contents of two typical lookup
tables. The first graph is for a lookup table where the values are arranged so that the output of the
camera increases linearly as the sensor output increases. The second graph is for a lookup table
where the values are arranged so that the camera output increases quickly as the sensor output
moves from 0 through 2048 and increases gradually as the sensor output moves from 2049 through
4096.
192 Basler pioneer