Pixel walk or pixel inversion occurs due to the display’s alternating positive and negative voltages that can sometimes manifest as different visual artifacts in regular use including gaming, watching videos, etc.
In order to avert picture burn-in or a build-up of static voltage, LCDs have to alternate between positive and negative pixel voltages (polarity inversion).
As a consequence, you might be able to notice certain visual artifacts in a form of interlacing patterns, including vertical lines, scan lines, and checkerboard, mesh, or grid effect – sometimes with color distortion.
Just how noticeable these artifacts are depends on the monitor’s panel and the content you’re watching.
For instance, pixel walk can be visible on a certain unit of a monitor, but not on another unit of the same model because every individual panel is at least slightly different.
It’s also possible that different units of the same monitor exhibit different artifacts on different type of content.
So, one unit of a monitor may have visible interlacing vertical lines on static content, while another unit of the same model might have an apparent checkerboard pattern with moving/dynamic content.
In all but extreme cases, this issue is not noticeable unless you’re looking at various test images that are supposed to emphasize these artifacts.
However, some monitors do seem to be more prone to this issue. Pixel inversion artifacts are more obvious and common with high refresh rate TN panel displays.
How To Test Pixel Walk
To test your monitor for pixel walk/inversion patterns, check out Blur Busters’ Inversion Artifacts tests.
You can also test it at lagom.nl where you’ll find a lot of additional and more in-depth information regarding pixel walk.
Avoid doing these tests if you’re sensitive to flicker.
Sometimes, ignorance is bliss. If you don’t notice any interlacing artifacts, these tests may point them out, and you might start noticing them in everyday use.
So, unless you’re just testing out a monitor or suspect that your monitor has too strong pixel walk that warrants an RMA, doing these tests may not be necessary.
How To Fix Pixel Walk
Depending on the particular type and cause of pixel inversion artifacts on your monitor, there are a few things you can try:
- Adjust the brightness and/or sharpness settings on your monitor
- Lower your monitor’s screen resolution, and then return the resolution to native
- Power cycle the monitor
- Reboot your graphics drivers (shortcut: Win + Ctrl + Shift + B)
- If your monitor is overclocked, reduce the refresh rate to native
- Turn off VRR (FreeSync/G-SYNC)
- Turn off backlight strobing (Motion Blur Reduction features)
- Adjust the monitor’s response time overdrive setting
- Let your monitor warm up (these artifacts tend to be more noticeable when the monitor is cold)
- Sit a bit further away from the screen (this obviously won’t fix the issue, but it’ll make it less noticeable)
Pixel walk/inversion artifacts can also easily be confused with other similar visual artifacts caused by FRC or overdrive.
Monitors with FRC (Frame Rate Control) use temporal dithering to alternate between different colors in order to ‘fill-in’ the unsupported colors by the display. This in-between color can sometimes cause a 30Hz flicker.
For instance, most lower-end TN and IPS displays use dithering to display 8-bit color depth (16.7 million colors) – that is 6-bit (262,144 colors) + 2-bit FRC.
Most people never notice this flicker, but you can sometimes detect moving patterns in darker tones. This can cause eye strain to sensitive people, but it’s very rare. Defective panels have far more obvious patterns.
You can also go to lagom.nl to test this out in the ‘Black level‘ test.
Response Time Overdrive
Monitors use overdrive to increase their response time (the speed at which pixels transition from one color to another).
With weak overdrive, you’ll get visible trailing or ghosting behind fast-moving objects, whereas too aggressive overdrive causes pixel overshoot (also known as inverse ghosting).
Some monitors will have the optimal overdrive mode set as default, and it will work ideally at all refresh rates.
However, with most monitors, you’ll have to manually find the best overdrive setting and it could be a different setting depending on the refresh rate.
For instance, using high overdrive may reduce ghosting at high refresh rates, but introduce inverse ghosting at lower refresh rates, which can be bothersome if you’re using a variable refresh rate technology such as FreeSync/G-SYNC.
You can again make use of Blur Busters’ motion tests to find the optimal overdrive mode for your monitor.