One of the biggest issues with accurate display calibration is the correction of volumetric non-linear errors.
And it is the correction of such volumetric non-linear errors that ColourSpace excels at, through the generation of highly accurate 3D LUTs.
Volumetric Errors
A term used a lot within this website is Volumetric when describing the accuracy of any display calibration. But what exactly does this mean, and why is it so important, and why can a 3x3 matrix not manage volumetric errors, as stated above?
Basically, a display has volumetric issues if it shows non-linearity errors within its gamut - essentially, the output of the display is not linear and predictable when the input signal is changed in a linear and predictable way between zero and 100% signal range. Potentially 0% and 100% may be accurate, but any percentage value in-between will contain an error.
So, 0% Green (black!) can be accurate, and 100% green can be accurate, but 20%, 52%. 76%, etc., Green can easily be inaccurate.
And that is the issue with a 3x3 matrix - it can never correct those in-between errors, as it has no volumetric capability. A 3D LUT is required to correct such volumetric errors.
More information on Volumetric Issues can be found in the HDR Volumetric Accuracy section below.
Assessing displays for underlying Volumetric issues
With ColourSpace, spotting underlying Volumetric display issues is extremely simple, as any good display should map to itself when in an uncalibrated, native state.
After profiling a display, the Modify option within the Manage Space library can be used to Extract the native colour space from the profile.
When the profile is mapped to the extracted colour space and non-linear Volumetric issues will become obvious, as for a Perfect display, each graph would plot 100% correctly, with every measurement plotted green, with zero dE error.
Any graph plot that is not perfect shows underlying non-linear Volumetric issue.
The above display profile, plotted against its own Extracted colour space, shows a range of Volumetric issues, with few measurements being green, and a very obvious bow/distortion in the blue to red gamut edge.
The EOTF plot shows few errors
RGB Separation shows serious volumetric errors, with major cross-coupling and luma issues caused by the individual RGB channels not tracking the equivalent grey scale value, or inaccurate grey scale values vs. the equivalent RGB primary values.
The unique 3D volumetric graphs within ColourSpace helps further in understanding just what the underlying Volumetric issues are.
Toggle the above graphs to also show the Tangents applied.
