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Bought a new graphics card a few days ago and decided to recalibrate both monitors on my rig. Both are Dell’s, one is U2717D, the other U2415. The sensor is a Spyder 5, I have the latest DisplayCal and installed the drivers from within it.
Everything went fine with the U2717. However, when I was setting the white point on the U2415 the green channel was quite low, and since the monitor setting was already at 100% on green I dropped blue and red to even things out. After the display calibration completed I noticed ***shocking*** disparity in the white point between the two monitors. The U2717 was normal, but the UI2415 was literally yellow. Per instructions from the FAQ I adjusted the white point on the U2514 manually, and now life is good.
However, I am still wondering how it is possible for such a large mismatch to exist. Things were not subtle, the whites on the U2415 looked as if they are illuminated by an incandescent light bulb. Prior to this graphics card update (gtx 1060 from Zotac) I had never noticed such a glaring mismatch. Any suggestions as to what I may be doing wrong? Other than the the fact that one of the monitors is connected via HDMI, the other via DisplayPort I have no clue what may be going on. This feels like it came out of nowhere.
Color instruments don’t “see” light as humans do. They use filters and individual sensors, usually red-green-blue (in the case of the Spyders, there are even seven color filters, but the manufacturer’s claim that this somehow “improves upon colorimeters that use 3-channel RGB sensors” – their words – is demonstrably not based in reality, in fact the opposite seems to be the case).
For that reason, what the human eye may perceive as visually different, a color sensor may regard as the same (in terms of measured CIE XYZ). The more accurate the instrument, the less these differences come into play, but colorimeter accuracy is inherently limited by design, which is why they are often paired with a spectrometer which is used to create a correction matrix for a particular display and colorimeter combination, which then improves the latter’s accuracy.
In the case of the U2717D and U2415, while they use similar backlighting technology (white LED), their gamuts are not identical, hinting at different generations or types of white LED backlighting being used, with potentially slightly different spectral distribution.
