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I noticed yesterday that none of my monitors were showing greyscale images correctly, edges were being enhanced, creating coloured ringing, not something desirable for an artist, such as myself (or anybody else doing colour-critical work).

This is the test image: , my monitor outputs the left edge as having a red hue, while the right edge is blued. In fact, the image is totally greyscale (you can check it with the colour selector in Paint). This is a photo of the test image on my monitor, the chromaticity should easy enough to see, .

It affects everything displayed on-screen, in every application. I have been through my monitor's settings, tried different monitors, and tried different computers with different graphics cards, so I am thinking that it is Windows itself that is doing this “enhancement”. I don't even know what this is called, much less, how to disable it. Can anyone help me out?

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Some tests here. Apparently, adjusting ClearType can help (in Win7, do it from the control panel) - but that might be for font smoothing only, and not images... – Bob Feb 2 '13 at 1:47
Cleartype is/was already disabled. – Eamon Moloney Feb 2 '13 at 1:48
Hmm. Are you connecting your displays via VGA, DVI, HDMI, DP? I'd lean toward hardware since Windows really ought not to be doing that. Surprising that it persists with totally different monitors/GPUs, though. – Marcus Chan Feb 2 '13 at 1:53
DVI (1 × single, 1 × dual) on PC (AMD video) and unknown laptop internals on the laptop (Intel video). – Eamon Moloney Feb 2 '13 at 1:56
up vote 1 down vote accepted

Okay, on second thought I looked at your photo again, and I hadn't realized how far you were zooming in. Any LCD monitor will have this issue; it's a result of the subpixel order, and the reason why subpixel rendering works, ironically enough.

Pixels under microscope

This photo (from is basically what you're seeing on the edges: since the blue or red edges of the pixels are on the edge, you can see them more, and so the edge of the images looks like it has a color tinge. (You could think if it as the blue, in this case, bleeding more into the darker area). You must have a pretty sensitive eye to notice something like that, especially if you have a high pixel density display.

subpixel graphic by me
(edit: better picture!)

This is basically what's happening. Even though there are the same number of red, green, and blue pixels, the red parts are all a little to the left and the blue parts are a little to the right. Thus, the edges have a little more of the color on that side.

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No, it's definitely not just my eyes, there is more blue on the right hand side than the left, I can measure it objectively in that photo using graphics applications. – Eamon Moloney Feb 2 '13 at 2:07
Yes, you're right, more red light is emitted on the left edge, and more blue light is emitted on the right. However, that isn't due to Windows (it looks like that on my Macbook screen, too, for example), it's just how the pixels are made in LCD screens. – Marcus Chan Feb 2 '13 at 2:11
I don't follow you. Just because the red sub-pixel is not on the edge it should not stop emitting light. There is always one red sub-pixel for every blue one, those sub-pixels will always balance in grey. The grey should never have colours. – Eamon Moloney Feb 2 '13 at 2:15
Let me finish my graphic in GIMP, one sec :D – Marcus Chan Feb 2 '13 at 2:15
I made an image myself… , there are definitely more reds and blues there full stop. it's not just an edge effect. – Eamon Moloney Feb 2 '13 at 2:21

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