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Old 08-01-05, 02:53 AM   #1
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Default ICC Profiling (and Twinview)

Does anyone know of any way to properly callibrate a monitor under linux? My monitors all look very strange and the inbuilt gamma in X11 doesn't do enough (my lights are green while my darks are blue .. !)

In my former life as a graphic artist, I used a spider-like device from Pantone, but that came with Mac software, not linux.

I have two external monitors that I attach to my laptop, (one at a time) One is a CRT which I expect to be able to callibrate correctly and the other is an LCD which I'd like to get as close as LCD will let me.

However the inbuilt monitor is completely different! So I'm hoping that there may be some way to get everything to play together and have multiple profiles, one for each physical monitor.

Does anyone know of good profiling software/hardware for linux that will play with my GeForce FX Go5600? (Even if there's a better way to calibrate by eye!)

Rick Measham
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Old 08-01-05, 11:36 AM   #2
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Default Re: ICC Profiling (and Twinview)

If you need some infos on setting different gamma settings to each monitor in a multi monitor configuration, take a look at my postings:
I don't know if it is possible to set the individual white point for each monitor but I believe not. The same for ICC monitor profiles. But if you find a way to use such profiles and if you have acces to a tool like colorspider, just create the profiles with Windows or MacOS and then use the profiles for your linux box; woul probably be the easiest (only) way.
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Old 10-28-06, 05:25 PM   #3
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Default Re: ICC Profiling (and Twinview)

Setting the monitor white point is a calibration step that is handled by setting the monitor controls (IE. changing the gain for the RGB guns). Monitor calibration and profiling goes like this (assuming you have a supported color meter or photospectrometer):

1. Set monitor contrast to max (to get most possible gain from the guns) using the monitor controls.

2. Set monitor black point by setting the monitor "brightness" control so that the guns turn on with any RGB values > 0. Most profiling software will use a color meter/photospectrometer to help the user set this.

3. Using a color meter or photospectrometer set the monitors RGB controls to get the desired white point (usually 6500K). Again the profiling software will assist the user with this step.

4. Run the profiling software to collect the information needed to set the video card gamma curves.

5. Use the vcgt information from step 4 to update the video card gamma tables. This is done by the profiling software. Steps 1 through 5 are the calibration steps.

6. The profiling software will run a set of samples and use that data to characterize the calibrated display and create the CLUT curves for the ICC profile.

7. Using the step 4 vgct information and the CLUT curves created in step 6 the profiling software will create a profile for the display.

Linux has some support for this and more support is on the way. Unfortunately you can NOT calibrate your monitors if you are running TwinView. The main reason is that with TwinView the video card gamma curves can not be set on a per monitor basis. In fact the API for doing this is not even implemented by the nvidia drivers for TwinView displays which means that the nvidia drivers in TwinView mode are not compliant with X11 standards for video drivers. Using Xinerama and not TwinView allows you to set individual gamma curves for each monitor.

Currently the only software that will support the above work flow in Linux is ArgyllCMS. This software supports a number of color meters/photospectrometers and can both calibrate and profile your displays. It also comes with a gamma loader that can be run at xwindows startup to apply the calibration data to your monitor/video card. Again this is not supported in TwinView.
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