Color management 3 – monitor calibration

For the CMS to be able to present images with correct colors on the monitor, (wich is – in my view – a must for any image manipulation) it must have a color profile for the monitor. Certain monitors ship with a factory default color profile, what is better than nothing, but you can create your own.

The easyest way is to adjust your display. A good explanation about it can be found in this article at linux.com. Although i can’t really agree with every point of its theory, the solution works, and is more or less accurate. This method won’t create a profile, but merely adjust your display settings, but it is better than nothing.

A better way is software-only “calibration”. Theese methods involve evaluating with our eyes, wich are not the most accurate measuring devices in the universe. The most widely known software of this kind is Adobe Gamma. You can guess if it is avialable in linux or not ;-). But fortunately, Monica and GAMMApage do the nearly the same (I must admit that so far I have not tried any of them, and it is not clear for me if they are just altering settings of x, or creating a monitor profile. Basically, calibration is not equal to profiling and therefore they are not likely to be albe to create profiles) as well as LPROF (i will post my experinece with LPROF at a later time).

The best way is to use a hardware calibrating tool, a so called colorimeter. Unfortunately, theese devices usually don’t come with linux modules. There are two workarounds. First, LPROF, and ArgyllCMS can handle several colorimeters. Second, on dual-booting systems, a profile created on one os can be used on the other as well (more on this can be found on Nicolas Vilars’s page).

Let me explain the process of creating a display profile with a colorimeter. Colorimeters can be used to calibrate and profile your monitor. Theese two functions are to be separated.

Calibration is the act of bringing a device to a known operational state. In the case of a monitor this includes two things: setting the white point of the monitor, setting the gamma (mid-tone) of the monitor. (this is the step you can do without a colorimeter)

Profiling is a process where the colorimeter and a software are used to determine the gamut a given display. Usually a series of colored blocks are displayed on the screen and measured by the colorimeter. The software uses the difference between the measured values and the original input values to determine the ability of the monitor to reproduce a wide range of colors. This range of reproducible colors is called the display gamut, or display color space.

After that a profile is created for the display color space.

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2 Responses to “Color management 3 – monitor calibration”

  1. Gerben Says:

    Someone is busy writing a driver for the ColorVision Spyder2 colorimeter: http://yan-ke.com/spyder/

  2. vivosz Says:

    Thanks, i know about it!
    And actually it was only the day before yesterday when i calibrated my notebook’s display with a Spyder under linux!
    Joel Cornuz dug into the topic and wrote a how-to on his blog:
    http://jcornuz.wordpress.com/2007/11/16/spyder-the-good-and-the-ugly/
    http://jcornuz.wordpress.com/2007/11/18/use-colorvision-spyder-to-produce-an-icc-monitor-profile-under-argyllcms-linux/
    The interesting thing was that i wasn’t pleased with the resulting profile, so i created another under windows. Much to my amazement the two profiles differ a lot!
    The problem must be somewhere in the calibration process (my display has no adjustment possibilities, and i think it is treated differently by argyll and the Spyder software) i think, but i must chew the argyll documentation to be sure.
    Anyway, i was pleased to read both Joel’s two articles (based on the link you’ve sent me and, one one from Ross Burton: http://www.burtonini.com/blog/computers/calibrated-2007-11-14-17-00 )
    and your comment. Thanks!


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