Why don't two calibrated monitors agree?

[Frank Petronio]

I use two NEC P221W monitors and a Spyder3Elite calibrator. I set both monitors to identical brightness, color temp, contrast, etc. and run the calibration routine. I use an 18% grey desktop background.

When I get all done, my Left Monitor is pinker and the Right Monitor is greener. Subtly, we're talking 2 points difference on the Photoshop Hue Saturation slider. But annoying.

I understand that my calibrator is software only and not tied to my hardware, it isn't like the fancy ones that give feedback to the monitor to produce a perfect neutral. But nevertheless - and maybe I'm having a brain fart or senior moment here - if I adjust my images to taste on one monitor, it will be different on the other. Doesn't this mean all this effort to calibrate is for naught and just a ballpark guesstimate, with at least a few points of fudge?

Or am I just in need of reeducation, some time spent working out in the Adobe fields where I can learn to become a proper digital citizen and go along with the prevailing dominant workflow?

[C. D. Keth]

Did both monitors get at least an half hour to warm up before your calibration and are you giving them at least an half hour to warm up before using them for color decisions?

[Frank Petronio]

of course

[C. D. Keth]

of course

Had to ask. Do both monitors have roughly similar numbers of hours on them?

[Amedeus]

What is the videocard you are using ? Spyder3Elite calibrator is fabricating calibration constants the driver routines are using to fudge the output. There are limits on how effective this is, all determined by the video circuitry but more importantly by the monitor. THe NEC you are using I believe has 6 bit LCD panels. This makes for 64 levels/color to be displayed. It only takes one level per color difference for the eye to see the difference on two monitors side by side.

Another source of mismatch is the aging of the backlight. CFL backlights have issues but so do LED backlights. The latter has typical binning issues that yields minor color differences. You won't notice on a single monitor but as soon as you put two side by side ... bingo.

If absolute color calibration is a must, then use LCD monitors with 10 bit panels and buy them from the same batch if possible to ensure best possible aging and binning of the backlight LED's. It should be said that 10 bit LCD panels give you much more room for proper calibration.

[Frank Petronio]

Thanks. These are the cheapest halfway decent monitors but no match for Eizos or anything good. I'm not really expecting a perfect solution, I know just to use one monitor consistently and use the other for tools, but I wanted to get an idea why it was happening and Rudi's explanation makes a lot of sense.

(Yes I bought them within two weeks of each other but they probably aren't from the same batch. And I am not using any sort of quality video card. Here is a long thread on my bargain system: http://www.largeformatphotography.in...l=1#post856818)

[Amedeus]

Looks like you have a fun system set-up with the Mac Mini Server. Many years ago I used a regular (slow) Mac Mini for PS2 for the longest time and yes, I calibrated my monitor with Spyder to match my printer. I still do the same on my 27" iMac and my laptop. The video card is not the bottleneck here, it's the monitor.

[Frank Petronio]

Well the onboard Intel video on the Mac Mini is what keeps it from being a great system... if Apple put a real video card (even on par with the laptops) then the Mini might cannibalize other sales so I "get it" but it is so close otherwise!

For now it is OK but as people move to higher-resolution displays and create more work for Retina-type displays, I feel kind of funny working on a desktop that is lower resolution than my iPad... it is a weird period of transition ahead for a couple of years.

[Light Guru]

Thanks. These are the cheapest halfway decent monitors but no match for Eizos or anything good. I'm not really expecting a perfect solution, I know just to use one monitor consistently and use the other for tools, but I wanted to get an idea why it was happening and Rudi's explanation makes a lot of sense.

(Yes I bought them within two weeks of each other but they probably aren't from the same batch. And I am not using any sort of quality video card. Here is a long thread on my bargain system: http://www.largeformatphotography.in...l=1#post856818)

Not being from the same batch could definitely contribute to the issue. However I'm suspecting that the issue is that you are using a Mac Mini.

Don't get me wrong Mac Minis are great little machines but the graphics card in them is simply not designed to run calibrated dual displays. The video out options on the mini do not allow for two monitors to be connected in the same way, you have one mini display port and one HDMI port. While there are some similarities in the connections they are still different connections.

Im not familiars with your particular monitors but I know that many monitors also have HDMI along with the standard DVI. With one of your displays connected via HDMI and one connected via DVI this could be the issue on the monitor itself. If the display handles those inputs slightly differently.

[timparkin]

Have you got any reporting on your calibration device? Most calibrations don't 'finish' with an accurate answer - they have a margin of error. If that margin of error is 1 point on the hue saturation slider (which is fairly accurate) then a 2 point difference would be possible. You might get a different result each time you calibrate the system too so it might make sense to try to calibrate the first one a few times, saving each profile, and choose the one that matches the best.