Viewing video card LUT curves
Viewing video card LUT curves
- Subject: Viewing video card LUT curves
- From: Marco Ugolini <email@hidden>
- Date: Sun, 06 Feb 2005 19:02:50 -0800
In a message dated Fri, 4 Feb 2005 13:18:09 +0100, Peter Karp writes:
> To check which calibration curves are active on the video card LUT,
> you can use the program "Gammas" which is found as an example
> application of the Mac OS X.
Hello, Peter.
You may know this already, but I thought I should mention, if nothing else
for the benefit of those who may not know this, that there is also another
way to review the calibration curves activated on your graphic card by your
monitor profile:
- Find your monitor profile (in your User -> Library -> ColorSync ->
Profiles folder);
- Double-click on it. That launches the ColorSync Utility.
- Once your profile is open in that application, scroll down to find the tag
called 'vcgt' (which stands for "video card gamma tag"). Click on it (just
once), and you will see a chart at the bottom of the window, showing each of
the three calibration curves that are being sent to the video card for the
Red, Green, and Blue video signal. You will be able to see only one of the
three channels at a time by selecting it in a pulldown menu right next to
the chart. These curves are EXACTLY the same as the ones you see via the
Gammas application (as long as you are viewing the monitor profile that is
actually being used by your OS at that particular time, of course).
Those who wish to study more in depth the internal structure of color
profiles can find more materials on the 'vcgt' tag (specifically at page
211) in Abhay Sharma's highly useful "Understanding Color Management" (along
with much else too).
Cheers.
Marco Ugolini
Mill Valley, CA
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