Vista Gamma Table Bug

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Description of the bug

A more serious problem, and this one is a show-stopper in my eyes, is the authorization bug. As you use Vista, you are occasionally interrupted by the OS as it confirms you have the admin-level privileges required or confirms certain actions. As a user-interface effect, Vista dims the screen slightly while offering the user a password dialog. Unfortunately, this dimming of the display clobbers the calibration curves in the graphics card and they are not replaced. So you startup Vista, your 3rd party utility loads your display calibration correctly but then 5 minutes into your session Vista requests some authentication and your calibration is gone... so you restart Vista, reloading the calibration and start out again.... It will be difficult to have confidence in a system's state of calibration.

Good blog discussion about the Vista gamma LUT bug

With Windows Vista, when you first load an ICC profile, the correct color and gamma settings are applied. But when you lock the screen, log off, or do a bunch of other things, the gamma LUT is reset.

There is no fix, at least none that we can see. When you lock the PC, your gamma table is reset.

There is a workaround (though a poor one). The freeware DisplayProfile utility (donate to help cover hosting costs!) will show you a list of available ICC profiles and let you switch between them on the fly, but more importantly, it will also apply the gamma table settings as well.


DisplayProfile is a standalone executable. Just run it and select a profile other than the one you want to use, then switch back to the real profile in order to re-apply the gamma LUT settings. Just stick it in your quicklaunch toolbar, and whenever you unlock your PC run it to reset the gamma settings.

This link will download the Display Profile program:

Report from Microsoft

There will not be a fix in Vista SP1, but the fix has been cleared for release as a Windows Update Hotfix shortly after SP1.

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