Features AW00123409000266 Basler ace USB 3.07.12 Luminance Lookup TableNormal ImplementationUsing the Luminance Lookup Table for Cameras with 12 bit ADC Data and PixelFormat Set for 12 Bit OutputWhenever the camera is set for a 12 bit pixel format (e.g., Mono 12), the 12 bits transmitted out ofthe camera for each pixel normally represent the 12 bits reported by the camera’s ADC. Theluminance lookup table feature lets you use a custom 12 bit to12 bit lookup table to map the 12 bitsreported out of the ADC to 12 bits that will be transmitted by the camera.The lookup table is essentially just a list of 4096 values, however, not every value in the table isactually 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 bits that will be transmitted out of thecamera when the ADC 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 bits that will be transmitted out of thecamera when the ADC 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 bits that will be transmitted out of thecamera when the ADC 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 bits that will be transmitted out of thecamera when the ADC reports that a pixel has a value of 24. And so on.As you can see, the table does not include a user defined 12 bit value for every pixel value that thesensor can report. So what does the camera do when the ADC reports a pixel value that is betweentwo values that have a defined 12 bit output? In this case, the camera performs a straight lineinterpolation to determine the value that it should transmit. For example, assume that the ADCreports a pixel value of 12. In this case, the camera would perform a straight line interpolationbetween the values at location 8 and location 16 in the table. The result of the interpolation wouldbe 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 havea defined 12 bit value associated with it. (Locations 4089 through 4095 are not used.) If the ADCreports a value above 4088, the camera will not be able to perform an interpolation. In cases wherethe ADC reports a value above 4088, the camera simply transmits the 12 bit value from location4088 in the table.The advantage of the luminance lookup table feature is that it allows a user to customize theresponse curve of the camera. The graphs below show the effect of two typical lookup tables. Thefirst graph is for a lookup table where the values are arranged so that the output of the cameraincreases linearly as the digitized sensor output increases. The second graph is for a lookup tablewhere the values are arranged so that the camera output increases quickly as the digitized sensor
