I already know the reasons for the use of hardware calibration but you never seem to know how to fix or know why when something goes wrong or be able to explain with authority why Ethan finds so many colorimeter packages vary from model to model and brand to brand in Delta E numbers.
Much of the variation we see is due to a combination of manufacturing inconsistency and lack of unit-by-unit calibration. For example, one of the best legacy sensors is the X-Rite DTP-94. It is hopeless on LED backlight or wide gamut dispalys, but on standard gamut CCFL models the manufacturing tolerances were sufficiently tight that the DTP-94 outperformed most other devices. DataColor appears to have made a silent upgrade to their Spyder3 colorimeters a year or so ago. They still vary more unit-to-unit that one would like, but not as badly as the initial units. The i1D2 could be individually calibrated - stock from X-Rite it wasn't - but that only masked some of the large variations between units.
Both of the newest sensors, the BasICColor Discus and X-Rite i1Display Pro, are constructed from the ground up to provide stable measurements. Both pucks are also individually spectrally calibrated before shipping.
As to why different monitor calibration products can create hue shifts when displaying blues or converting from PP RGB blue to sRGB blue, that depends on how they render colors that are not only out-of-gamut, but mathematical fictions in a real-world monitor color space. All the PP RGB primaries are imaginary colors; i.e. they do not correlate to any physical color that can actually be created. Needless to say, your monitor can't display these colors accurately. In fact, almost 15% of ProPhoto RGB colors do not map to physical, real-world colors.
The sRGB blue primary is not an imaginary number, but does fall outside the gamut of most monitors, even wide-gamut models. I have no experience with SuperCal. It is very possible that it simply maps working space primary colors to the monitor primaries. This is neither mathematically nor visually accurate, but it will prevent color shifting when converting primaries between color spaces with vastly different gamut volumes. A pertinent question is: does this matter? After all, you will never encounter a PP RGB blue primary in the wild and the chances of finding even a pure sRGB blue are vanishingly rare. Graphic illustrations are another matter entirely. Spot colors is one of the reasons Adobe sells Illustrator to complement Photoshop.
