Lookup Table (LUT) is a common image processing technique to map a pixel from one value to the other. The camera has an 11-bit input lookup table that produces 9-bit output. When a pixel value is larger than the 11-bit maximum (i.e., 2047), LUT treats it the same as the 2047. The LUT is available for all pixel formats.
- When outputting 8-bit pixel formats, the 9-bit LUT output is rounded down to the 8-bit value.
- When outputting 12-bit pixel formats, the 9-bit LUT output stays as the most significant 9 bits of the 12-bit value and the remaining 3 bits are all zeros.
- When outputting 16-bit pixel formats, the 9-bit LUT output stays as the most significant 9 bits of the 16-bit value and the remaining 7 bits are all zeros.
Therefore, LUT should be used cautiously for 12-bit or 16-bit pixel formats since some of the least significant bits are thrown away.
The factory default LUT is the linear mapping after the camera powers on (P' = P/4).
To customize a LUT:
- Use the LUT Selector to choose which LUT to control. LUT1 is the only lookup table to allow user access and control.
- Use LUT Enable to disable the selected LUT before customizing it. Customizations of the LUT apply immediately, therefore an active LUT that is changed may result in unexpected images.
- Use LUT Index to identify the index (offset) of the coefficient to access.
- LUT Value returns the value at the entry of the LUT Index. Enter the new value.
- Repeat steps 3 and 4 as necessary.
- Enable LUT to have changes take effect.
For coding purposes, LUT Value All provides access to all the LUT coefficients in a single string without using an individual LUT Index.
Since only one LUT is available for users to access and control, in RGB and YUV pixel formats, the same LUT applies to all three channels (i.e., red, green and blue). In monochrome and Bayer formats, there is a single channel, regardless of the color or monochrome image sensor.
Note that the customized LUT is not saved into the camera permanently. After power cycling, the LUT returns to the factory default.
|LUT Selector||IEnumeration||Expert||Selects which LUT to control.|
|LUT Enable [LUT Selector]||IBoolean||Expert||Activates the selected LUT.|
|LUT Index [LUT Selector]||IInteger||Guru||Control the index (offset) of the coefficient to access in the selected LUT.|
|LUT Value [LUT Selector] [LUT Index]||IInteger||Guru||Returns the Value at entry LUTIndex of the LUT selected by LUTSelector.|
|LUT Value All [LUT Selector]||IRegister||Guru||Accesses all the LUT coefficients in a single access without using individual LUTIndex.|
LUT Control Features
Selects which LUT to control.
Activates the selected LUT.
|Name||LUTEnable [LUT Selector]|
Control the index (offset) of the coefficient to access in the selected LUT.
|Name||LUTIndex [LUT Selector]|
Returns the Value at entry LUTIndex of the LUT selected by LUTSelector.
|Name||LUTValue [LUT Selector] [LUT Index]|
LUT Value All
Accesses all the LUT coefficients in a single access without using individual LUTIndex.
|Name||LUTValueAll [LUT Selector]|