A few days ago I invested in an X-Rite i1 Display 2 colourometer, as per this answer, although I'm having great difficulty getting a Dell U2412M and a Dell E1911 monitor to the same whitepoint. I've tried the software that the device came with and a demo of another piece of software (I can't recall the name unfortunately). I have settled on a piece of free software called Argyll CMS along with the GUI frontend dispcalGUI, as it seems a little more capable; however, this is simply my impression of it.
I'm aware that there will be differences in quality between the U2412M and the E1911, although I'd have thought that after calibrating the monitor and creating a high quality profile for both monitors that the difference would be next to impossible to detect with the eyes. However, there is a very noticable difference in the colours the two monitors show. The U2412M seems to have a slight red tinge to it, while the E1911 has seems more of a grey tinge.
The calibration settings I've used for both monitors is as follows:
Whitepoint: 6500K White level: 120cd/m2 Black level: Native Tone curve: 2.2 Calibration quality: High Profile quality: High Profile type: Curves + matrix Testchart file: Large testchart for "curves + matrix" profiles.
I have control of the brightness, contrast and individual RGB channels, so I'm able to calibrate the monitor before using a profile. I've put up links to the profile verification reports for the U2412M and the E1911. You can see that each monitor seems to struggle with particularly blue colours.
Obviously there is no way you can see the actual colours displayed by the monitors, but as I said, it is quite a noticable difference. I know this is a little open-ended, but could anybody suggest what may be going wrong here, or have I just got bad quality monitors?