Yes, you're absolutely right. Spyder5EXPRESS doesn't calibrate the monitor's luminance. This is a feature of Spyder5PRO and Spyder5ELITE. My advice was to help Eric avoiding any influence from other light sources, which can be the ambient light, but also just stray light from the other monitor. And the brighter the monitor's luminance is, the lower is the influence of other light sources shining on it's surface (in relation). The best way would be to calibrate the displays again (with FullCAL on Spyder5PRO/Spyder5ELITE - Spyder5EXPRESS has FullCAL only) in a pitch dark room and covering the other monitor's screen while calibrating. The gamma setting is irrelevant for color management purposes, it will get remapped and you will see no difference. Setting gamma is mostly about getting the monitor to perform its best, so it should be set to the native value (usually 2.2). But it could in theory be anything and there would be no difference, as long as the corresponding monitor profile describes that response correctly. For applications without color management, gamma has a direct visual impact. Matching two displays of different brand and model is very difficult and is not a question of setting identical white point values. They usually need to be very different to achieve the same visual appearance. Trust your eyes, nevermind the numbers. Use the color of white paper as a common reference, and let the numbers fall where they want. No, this is not correct. Yes, the gamma will be corrected, but this will be done with squeezing the tone response curve. Having corrections from a monitor's gamma 1.8 to a value of 2.2 (sRGB/AdobeRGB) it will end up in loosing details in shadows and highlights due to the compression that affects these ends. That's why Spyder5PRO and Spyder5ELITE  are including a feature called MQA (Monitor Quality Analysis). This allows you to pre-calibrate your monitor as best as possible (means finding the closest matching Gamma setting, color temperature setting and setting the luminance). In addition to that Spyder5ELITE has an extended MQA which also measures the uniformity in terms of luminance and color output of a display. Matching two different displays is a challenge, but it can be done very closely. Here's how to do that: calibrate both displays to a certain target (normally gamma 2.2 and 6.500k color temp use Spyder5ELITE's feature StudioMatch to bring them technically as close as possible to the target and to each other after the calibration sit in front of your monitors the way you will do while processing your images open SpyderTune and compare the shown test images. Often your 2nd screens looks a bit color tinted. This is because your eye/brain compensates the light spectrum of the main display right in fron of you. Now use the purple-green and blue-yellow slider of SpyderTune to adjust the 2nd screen until it matches the primary one as best as possible. Done. 😉 ... View more

Spyder5EXPRESS can calibrate two monitors on a system. That's not the problem. You still need to know a little bit about using two screens on one graphic adapter: Each profile created has two parts, one part will be used by the colormanagement of windows and the other part will be loaded into the Lookup-Table (LUT) of your graphic adapter. This is what SpyderUtility does on boot-time. See the LUT as a kind of translation table for creating the right colors. To calibrate and use two screens on one system, you need to ensure using a graphic adapter with two separate Lookup-Tables. If your graphic card has two separate LUTs can not be seen from the outside and you should ask you vendor or the manufacture of your adapter. Most modern video cards are including multiple LUTs. Additional things that you should know and do: Please give it another try and make sure to work in a dark room: Set both displays to the highest brightness level. Now, make sure to calibrate (FullCalibration) both displays to the exactly same target values for: - gamma - whitepoint - brightness But since both displays are never exactly standing at the same spot in the workingspace, there could be different ambient light which may also influent color calibration and color appereance. They can even influence each other (shining on the other screen). Try to avoid this as best as you can. If both displays would operate via one and the same computer, you should match their different luminance levels with the StudioMatch feature of Spyder5Elite. Another useful tool to match the color output is SpyderTune which is also included in Spyder5ELITE. SpyderTune allows visual compensation of different monitor types. Newer displays often use LED backlight while others (mostly older ones) use CCFL backlight. These are physically different light sources which produce a very different light spectrum. But this is only an issue while you are looking at both at the same time. Human eyes are able to compensate one type of light source at the time. Once you are looking at each display separately, the eyes will via the brain automatically adapt to the appropriate light spectrum - so simply use SpyderTune (it's also a part of Spyder5ELITE) to match it as close as possible. Thanks, Oliver ... View more