With the desire to have fast profiling, low cost, and colour accuracy being a bit of an oxymoron, an alternative method is needed to increase the colour accuracy of faster, and cheaper, colourimeter probes.
This is performed by calibrating, or matching, a colourimeter based probe to a spectroradiometer on the same display.
In this way the colourimeter is accurately matched to the spectroradiometer for the specific display to be profiled, producing more accurate results.
There are two different methods available for probe matching - 4 Colour Volumetric Matching (FCVM), and Multi-point Volumetric Matching (MPVM).
ColourSpace doesn't use the older, traditional, 4 Colour Matrix (FCMM) Method for probe matching, as the volumetric approach offers far greater probe matching accuracy.
Probe Matching Benefits
Using probe matching, the speed benefits of a colourimeter, and more importantly the lower-light reading capabilities, can be employed while simultaneously enjoying the greater accuracy of a spectroradiometer.
4 Colour Volumetric Matching
4 Colour Volumetric Matching (FCVM) is based on the older, and traditional, 4 Colour Matrix Method (FCMM), but provides a greater level of accuracy, and is unique to ColourSpace. For the majority of displays it is all that is required for accurate probe matching, including non-additive displays, such as LG's WOLEDs.
- Attach the first (colourimeter) probe, selecting standard probe parameters as required from Probe Options
(A None/Bypass/Default pre-set within the colourimeter should be used, not a display specific matrix pre-set)
- Select the Probe Matching option, and press New
- Enter a unique descriptive name and press OK
(Use a name that includes the display and probe details)
- Place the probe on the patch window and press Measure All
(The patch window will cycle R, G, B and W patches, and save the probe/display measurement data)
- Change the probe to the second (spectro) probe, and repeat the process
(Spectro's do not use matrix pre-sets)
The order the probes are measured in is not important, and you can measure the spectro first, with the colourimeter second.
- If using a separate patch window, not controlled via ColourSpace, use the RGBW << Measure buttons in-turn
(Each patch colour should be based on a value of 240 to match the ColourSpace generated patches on 0-255 range (8-bit), and 222 for 16-235 (8-bit), although this is not critical so long as the same exact patch values are used for both probes)
- With the probe placed on a patch of the correct matching colour press the relevant << Measure button to take a measurement
(When White is measured the Luma value will be updated too)
- Alternatively, manually enter the xy values, remembering to record the Luma value when reading white
Regardless of the procedure used to take the probe measurements, the profile files are used in the same way.
- Select the spectro Reference Probe/Display Preset file from the Probe Matching lower drop-down menu
- Select the colourimeter Active Probe/Display Data file from the upper drop-down menu
- The colourimeter measurements can now be corrected to match the spectro using the Probe Matching Active tick box with Graph Options, Processing
Multi-point Volumetric Matching
Multi-point Volumetric Matching (MPVM) is also unique to ColourSpace, and as the name suggests uses more than the 4 colour measurements of the above 4 Colour Volumetric Matching method. This is aimed at displays that have a serious non-linear volumetric colour response, with spectral colour variations throughout the display's brightness and colour range.
The fundamental difference with Multi-point Volumetric Matching is that the entire display's colour volume is profiled to perform the match, not just 4 bright patches.
- For Multi-point Volumetric Matching a profile really needs to be cube based
(Multi-point Volumetric Matching will work best with uniform profiles, not random ones)
- Best results will be attained when the display peak white is set to be close to the target peak white
(For example, 100 nits for SDR calibration)
- Profile the display with each probe in-turn as normal, with no probes selected with the Probe Matching, Configure option
(Use a None/Bypass/Default pre-set within the colourimeter, not a display specific matrix pre-set)
- After profiling both probes, open the Space Management library, and use Modify, Extract BPD to convert the profiles into Probe Matching files
(Use a descriptive name for the extracted BPD file)
The probe matching files can now be selected within the Probe Matching option, exactly as for 4 Colour Volumetric Matching.
Application of Probe Matching
With the unique Post-Profiling application of probe matching within ColourSpace, any saved profile can have any probe matching applied as desired, at any time after profiling has been performed.
When performing Manual Measure adjustments probe matching needs to be performed on the live measurements, not post-profiling.
With ColourSpace, probe matching for both pre-and-post profiling is equally applicable.
For any probe matching process - Manual Measure, or Post-Profiling - simply set the Probe Matching options within the Probe Options menu, and enable matching when required via Probe Matching Active within Graph Options. Any probe readings, both live measurements and saved profiles, can therefore be displayed with or without probe matching applied, as desired.
When a profile is saved into the library, the status of Probe Matching Active is applied to the saved profile. It is therefore recommended to use a profile name that states if Probe Matching was active, or not, when the profile was saved, to prevent double application of Probe Matching.
If Probe Matching is being used, the profile MUST be saved with Probe Matching Active for use with LUT Generation.