Color calibration is only affecting one monitor in a dual display set up.

I just updated to ML and found I am having the same issue. When I tried to apply a new display profile on my second monitor the changes happen on my primary monitor. I am using an early 2009 Mac Mini with twin Samsung 172x displays. I have been using this configuration since 2009 without issue.

I have the same problem here. As long as I used 10.6.8 everything worked fine but after the 10.8(.2) update I can only change the left monitor (even if I do modify the right monitor color settings).

I've an MacPro connected two Samsung 215TW monitors, one via DVI and the other using an (apple=expensive) active minidisplayport to dvi adapter. (And I also have another active minidisplayport to dvi adapter which is connected to my projector, because it's only possible to use three monitors when using two of those active adaptors).

I've searched the net and found that using /System/Library/Displays/Overrides some settings can be changed, but I found no help to make the two monitors less identical so the system would work better.

Infos about it, e.g.:

http://www.insanelymac.com/forum/topic/208410-fixing-scrambledstretched-or-wrong -resolution-laptop-display-problems/page__st__0

Now I've figured out that both monitors are totally identical which means that also the serial number within the EDID information of the monitors is identical. Which also seems not unusual as the Eizo monitors we have at work do all have the serial number 0. And is seems that that's the problem.

(To view your setup run "ioreg -l" in the terminal and search for "AppleDisplay" and you'll see all your displays.)

Unfortunately there is no easy solution to change that.

Why has Apple changed something since 10.6 that those no longer work correct?

I checked, mine also share the same "DisplaySerialNumber" but the id number listed at the top is different.

Apple System Profiler > Graphics & Displays

About this Mac > ( More Info ) > Graphics & Displays...

.. will also list the details of each attached display.

You're only half right (as I just found out).

According to the System Information (formerly System Profiler) I have those serial numbers:

- HS6PB00038

- HS3PB00521

But according to ioreg I have those:

- 1146106417

- 1146106417

Then I've examined the EDID data of both monitors (http://en.wikipedia.org/wiki/Extended_display_identification_data).

The first serial numbers are within an extended descriptor (EDID Other Monitor Descriptors) and the ones ioreg is displaying are from the field "Serial number. 32 bits, little endian" (Bytes 12-15)

So either Apple displays those neat long serial numbers but don't care and uses only those from ioreg or OS X can not handle two monitors with identical Vendor/Product at all.

I can confirm system profiler shows different serials while ioreg shows the same.

System Profile:

SyncMaster:

Resolution: 1280 x 1024 @ 75 Hz

Pixel Depth: 32-Bit Color (ARGB8888)

Display Serial Number: HMEX603897

SyncMaster:

Resolution: 1280 x 1024 @ 75 Hz

Pixel Depth: 32-Bit Color (ARGB8888)

Display Serial Number: HMEX900057

ioreg -I:

"DisplaySerialNumber" = 1146302775

"DisplaySerialNumber" = 1146302775

Hi, I've had this issue since I've updated from 10.6 to 10.7 and its definitely a bug in the system. The ONLY solution that Worked for me : use 2 DIFFERENT displays.

This is what I have :

Mac Pro (Early 2008), 2 x 2,8 GHz Quad-Core Intel Xeon, RAM 16 Go 800 MHz DDR2 FB-DIMM, Graphism 2x ATI Radeon HD 2600 XT 256 Mo

Mac Pro, OS X Mountain Lion (10.8.2)

I'm running 3 different displays...

I first ran into this problem when upgrading to Lion. Now on ML and still have this issue. Apple - why have you penalized those who are using identical manufactuer dual montior setups? Please, please fix.

Dual Samsung SyncMaster 244T

ATI Radeon HD 4870

This is very annoying, but this workaround helped me: just briefly change the primary display (drag the menu bar to the other monitor in Arrangement). Then you can set the color profile on that one and change back.

No fix with the latest update 10.8.3.

Hi,

I also wrestled with this problem for a long time now but I think I found a solution.

I'm using:

- MAC pro 2x2.4 Hgz quad core intel xeon

- Software is 10.7.5

- X-rite I-display pro screen calibrator

- 2 x 24inch screen Samsung Syncmaster BX 2440 connected via DVI connection. Exactly the same screens

So what have I done:

Step 1

- Shut down MAC

- Connect only screen #1 to output 1

- Calibrate that screen with X-rite and save profile under something like screen-1

- DO NOT TOUCH ANYTHING under screen preference like colors etc

- Close all prg's and shut down computer

Step 2

- Disconnect screen 1 - or switch off so MAC only sees 1 screen

- Connect screen #2

- Calibrate that screen with X-rite and save profile under something like screen-2

- DO NOT TOUCH ANYTHING under screen preference like colors etc

- Close all prg's and agin shut down computer

Step 3

- Now Connect both screens to the cables or connection on which you did the calibration. so no swapping.

- Start up your MAC

- Your colors now should look exactly the same on both screens.

- Done and DO NOT TOUCH ANYTHING under screen preference like colors etc.

On my siutation the result was excellent. I always had problems with inconsistant colors between the screens. Left screen was always greenish and teh right screen always reddish instead of grey.

If this procedure is OK for other situations I really do not know but I thought I let you all know and maybe help.

regards

Andre (from Holland :-)

Ugh. This is affecting me as well. Makes me wonder if it's a video card or software issue (I have the GT 120). OSX sees my monitors as TV's, not sure if that is contributing to the situation.

My screen that's attached to DVI will not adjust. Any selection of color profile has no effect, and the profiles are linked across the monitors. So If I select one for the right monitor, the selection changes, but the monitor doesn't, but the left one does. It doesn't matter which screen I select it, it changes on both, but only one monitor actually changes. Frustrating.

Just crazy. WAAY too much work. But perhaps I'll try.

I too am running two different displays on an early 2008 MacPro that I just upgraded to Mavericks : bad move, I fear. Apart for a bunch of software and hardware drivers not working anymore, my displays are not the same color! My Samsung flat screen is ok but my old CRT (Dell) is...green! I mean r-e-a-l-l-y green. It ran fin while I was on OS X Snow Leopard (10.6.8) but now I can't get the CRT to look "normal". I have an ATI Radeon video card.