Poor LUT processing, be that within a monitor, LUT box, or grading systems, can cause unexpected results.
The use of Active LUT vs. the Uploaded LUT via verification can show such issues.
LUT Processing
LUT Processing errors are caused by poor signal processing within the display, LUT box, or graphics program, causing the output of LUT to be incorrect. A good example of this was the BMD HDLink Pro, which distorted any LUT loaded into it.
Unfortunately, some displays have similar issues.
The following shows just the grey scale (RGB Balance) results of the same calibration LUT verified within ColourSpace via Active LUT vs. the same LUT Uploaded into a display. As can be seen, the Uploaded LUT shows significant errors that are not present in the Active LUT verification.
The above comparison clearly shows that the LUT processing within the display is distorting the LUT calibration accuracy. While only RGB Balance is shown, similar errors will exist throughout the volumetric colour, and not just in the grey scale.
Unfortunately, such issues can only be overcome by the manufacturer correcting their image processing.
(While it may be possible to concatenate multiple LUTs, generated from multiple profiles with each LUT Uploaded, the results will never be ideal/accurate.)
The above assumes the TPG is accurate, as an inaccurate TPG will itself cause calibration issues.
See Signal Processing for information on signal processing issues.
