Monitor Calibration with 2 computers

[ATJ]

I currently have 2 laptops connected to my 22" LCD monitor, one running Windows 7 and the other Mac OS X. I calibrated the monitor for my MacBook Pro using the Advanced option with Eye-One Match 3 (Mac version). In that procedure you adjust the Red, Green and Blue channels in the early part of the calibration. I had to add a lot of blue.

Next, I calibrated the monitor with the Windows machine, also using Eye-One Match 3 but this time the Windows version. I didn't use the advanced method as realised this would force me to change the RGB settings. Even after calibration every thing looks blue.

Is it actually possible to have a monitor calibrated for 2 different computers? If it is, how do I go about it?

Edit: Corrected typo in Subject. It's going to take me a while to get used to the Mac keyboard.

[Steffen]

The problem with calibration (i.e. forcing the display to conform to certain white point and gamma) is that the necessary changes are often split between the monitor and the graphic card's LUT. Calibrating the monitor by changing its RGB gains also reduces its gamut and overall contrast/brightness. I usually run monitors at their native white point and gamma which with "good" monitors is pretty close to D65 and 2.2. I then generate an ICC profile for the graphics card/monitor combo using a colorimeter so that all colour management aware software (all of OS X pretty much) will correct for their flaws and make images look the same on all computer-monitor combinations.

Cheers
Steffen.

[ATJ]

I usually run monitors at their native white point and gamma which with "good" monitors is pretty close to D65 and 2.2.

How do you do that? Isn't that what the first step of adjusting RGB does?

[Murray Foote]

Just fishing, here, because I'm not sure of the answer.

In my case I have two NEC monitors with automatic hardware calibration but I don't run my laptop of a larger monitor. My two profiling systems are NEC Sprectraview 2 and Coloreyes. These days I would only use Coloreyes to profile the laptop itself but I haven't got round to doing that yet.

If you calibrate and profile your monitor, you end up with a file that gets loaded when your computer starts up. You can make a different file and choose either as appropriate. My presumption is that that file will include the calibration as well as the profiling. If I wanted to choose a different file I would select that through the Spectraview 2 interface. I should also be able to do that using Display colour management in the Windows Control Panel. I'm not familiar with Mac colour management.

My presumption is that you would calibrate and profile on your Mac laptop for one profile that will appear with that laptop and both calibrate and profile again for your Windows laptop for the profile that will appear for that laptop. Then as long as my presumption is correct that the calibration is incorporated in the profile, then your screen will appear correctly irrespecive of what laptop you connect.

[Steffen]

Yes, this is typically how it works. During calibration (i.e. adjusting the hardware to a known set of parameters) three kinds of settings can usually be played with: You can manually turn (virtual) knobs on the monitor, the calibration/profiling software that comes with the colorimeter can adjust the video card's look-up table (LUT) and you can change the LUT yourself via some video driver utility. Calibration can consist of any or all of these. If you use calibration software to make LUT adjustments then those will normally be stored as part of the ICC file that's generated during profiling and loaded into the video card every time colour management starts up.

After calibration the whole setup is profiled (measured for its actual response to input values) and the profile can be used by CM aware software to compensate for deviations from the response defined by the various colour spaces. The profile is only valid for the exact same calibration of monitor and video card it was obtained for, of course. Therefore neither monitor nor LUT settings must be touched after profiling.

Monitors used with more than one system should be calibrated to the most universally agreeable setup that doesn't limit their overall brightness too much. SInce the RGB adjustments inside the monitors often have 8bit or worse granularity as little as possible should be adjusted so that the dynamic range isn't restricted in any of the channels. If there is no "native" white point setting I'd calibrate for the pre-defined sRGB and gamma 2.2. Then, all computer-monitor combinations need to be profiled and should produce reasonably identical image colours under colour management. In some OSes (like Win XP) the GUI elements themselves aren't colour managed, so the desktop may still appear different from system to system. However, photos in Ps or Lr should be fine. The OS X GUI and Safari web browser are fully colour managed, and I presume Windows 7 is too.

Cheers
Steffen.

[ATJ]

If there is no "native" white point setting I'd calibrate for the pre-defined sRGB and gamma 2.2.

What I'm is asking is how do I go about this part? How to I calibrate to a pre-defined sRGB and gamma 2.2?

It was my understanding that when I was doing the advance calibration and it had me change the RGB values, I was actually setting up the white point. I completely understand that this may make it more difficult for the subsequent steps, but how else do I set this white point?

Or do I just set all three RGB to their midpoints and hope for the best?

[Murray Foote]

This may depend on part on your profiling software. I presume you have a full version of Match because the lesser versions of i-1 offer restricted choices.

You should be able to set Gamma but I can't see anywhere in Spectraview II or Coloreyes where I can specify a gamut such as sRGB.

You were initially calibrating only for one profile. Does it work with my suggestion to do a full calibration and profile for each laptop and then switch between them.

[Steffen]

If there is no "native" white point setting I'd calibrate for the pre-defined sRGB and gamma 2.2.

What I'm is asking is how do I go about this part? How to I calibrate to a pre-defined sRGB and gamma 2.2?

It was my understanding that when I was doing the advance calibration and it had me change the RGB values, I was actually setting up the white point. I completely understand that this may make it more difficult for the subsequent steps, but how else do I set this white point?

Or do I just set all three RGB to their midpoints and hope for the best?

Sorry, I should have said "pre-defined D65 and gamma 2.2". Most monitors have those presets, sometimes they're called "sRGB", sometimes you pick a colour temperature (6500K) and gamma separately. If there are no presets at all I'd start will the factory defaults.

Beware that some monitors can't be calibrated properly and resist profiling as they change their setup dynamically to match the screen content. Those monitors often quote excessively high contrast ratios like 5000:1 and higher.

Cheers
Steffen.

[Steffen]

You were initially calibrating only for one profile. Does it work with my suggestion to do a full calibration and profile for each laptop and then switch between them.

Very few monitors can actually be calibrated to match a certain profile, those that do come with hardware support for colorimeters and perform high-bit internal colour mapping (high-end Eizos etc). With most monitors all you can calibrate is the whitepoint and the gamma. That's fine for most purposes because once you've obtained a profile for the video card/monitor combo colour management can compensate and takes care of making the output match a particular colour space.

Cheers
Steffen.

[ATJ]

Sorry, I should have said "pre-defined D65 and gamma 2.2". Most monitors have those presets, sometimes they're called "sRGB", sometimes you pick a colour temperature (6500K) and gamma separately. If there are no presets at all I'd start will the factory defaults.

OK, there was a preset for "sRGB". The other choices were "Blueish", "Redish" and "Neutral". I went with "sRGB" and then calibrated with each machine without changing the monitor.

Thanks.