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it's most noticeable when the screen is displaying mostly black or dark imagery (in games, videos, fullscreen photoshop, content doesn't seem to matter) - and it seems like both monitors are slowly flipping back and forth between a slightly lighter and slightly darker black tone. you can't see it at all in bright images, but dark ones are shifting back and forth every second or so.

(displays are ASUS VH236H, run through DVI by a GeForce GTX 560)

edit - after fiddling around a bit more, I discovered that this only happens when the monitor is set to 'game display mode' using the onboard settings (not the windows or nvidia settings, but the stuff build into the monitor itself, alongside brightness + contrast etc) - I've tried messing with ASCR mode (aka dynamic contrast) and that doesn't seem to make a difference.

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This used to happen to me on my GTX 560, but only in Windows 7 (and not in Ubuntu). Turned out that adaptive brightness was on.

(I'm assuming you're running windows)

Type services.msc in your start menu and click the first result. Then find Adaptive Brightness and disable it (Right Click --> Properties, select Disabled from the drop-down menu and then click the Stop Button).

There might be a setting in Power Options (via the Control Panel) but I'm not 100% sure.

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  • good suggestion, but it looks like that service isn't currently running, and it's still happening. I went ahead and disabled though, we'll see if that makes a difference. – matt lohkamp Aug 13 '14 at 21:39
  • Adaptive brightness is for when we have direct control of the backlight, such as with laptops and tablets. Brightness on desktop monitors is controlled by the monitor itself in almost all cases. – Spooler Sep 26 '16 at 0:21
  • for what it's worth, 4 years later... I no longer notice this happening, and I have no idea why. I'd accept your answer, but I can't really be sure that disabling the service was what fixed it. :\ – matt lohkamp Aug 3 '18 at 2:15
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You're experiencing a common technique used to preserve the life of underprovisioned backlights in CCFL and LED monitors. Some manufactures adaptively vary the backlight to have more current during very dark display times (mostly black) and less backlight current during mostly white displays. The idea being that most of the time people will not be using it to display very dark scenes for long periods of time.

This is usually paired with underprovisioning the backlight as a method of being "green". What it is instead is cheap with a green disguise (as most of these things are).

SO if you are displaying dark scenes for a very long time, the controller will have to "give up" on over-volting the backlight when it overheats, causing a sort of periodic shift between bright and dark.

You should be able to play with your monitor setting to set the overall brightness down, taking a load off of the backlight in general. However, no degree of that will be enough if the backlight is grossly underprovisioned. Dunno if it is in your case, but it's worth fiddling with.

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