Mac Mini (M1) 2020, LG UHD monitor flickers on dark colours.

I also have the LG 32 UN500-W and have the same flickering issue.

When I boot the Mac mini, the sign on page background is all vertically lined (corrupted) until I sign in, then it's OK.

Also, if you visit this page: https://www.blackmagicdesign.com/products/davinciresolve/ there is a video playing at the top of the page, it causes terrible flicker.

I can get rid of the flicker if I go into the monitor settings and change the black level to "High"

(Picture -> Picture Adjust -> Black Level - High

Although this works, I would prefer not to have to set this, I don't like the look as much, the blacks look washed out.

Seems like a software issue to me.

Regards,

Derek

Done some further testing and I am 100% sure its nothing to do with grounding, I removed all USB devices also disabled wifi & bluetooth, just had the Mac mini and screen connected up on a page I know to flicker like crazy. Nothing made a difference grounding the Mac mini and removing ground from the monitor didn't even make the picture change at all nor did adding and removing USB devices.

For me to fix it : adjusting the 'sharpness' on the monitors pictures settings from a default 5 to a 7 totally fixes the issue , again same webpage on the screen it changes from flickering with lines down the screen to perfect. The same also works if you adjust to a 3 but 7 gives more detail.

Something else that also works is changing from HDMI RGB PC Range from Auto Detect to 16 - 235 (full is 0-255) you don't want to do this though as it meant for using the monitor to watch films/DVD you loose grey levels.

There is def something wrong with the GPU in the M1 reacting with certain monitor settings, I also tried different refresh rates using switch res x and resolutions, nothing makes a difference.

The sharpness trick seems to have the most effect and fixes it .... will report back if it happens again with it on sharpness 7.

Hi all,

same problem here with mac mini m1 and BenQ PD2700U with display-port (the problem isn't the monitor)

The problem starts only if OS is in dark mode. BigSur 11.2.3 (20D91) and previous versions

Tried to connect and disconnect but nothing. The only solution is to put in light mode.

Softwares in dark mode don't cause flickering issue.

I had this issue as well with a new Macbook Pro 16" M1, and an LG 34WL60TM ultrawide monitor. With my desktop background set to gray, I would see the flickering wherever there were shadows around the borders of windows. I was able to get rid of it by setting the monitor refresh to 60Hz (recommended by the monitor), and in the monitor's picture settings, setting the Black Level to "High":

Settings > Picture > Picture Adjust > Black Level: High

With this set to Low (default for the monitor), the flickering is always present.

Just wanted to add my experience with this problem here.

I have a Dell S3221QS 4k/32 inch monitor and an M1 Mac Mini and have been getting this same problem in varying degrees depending on settings - vertical lines appearing in darker areas, which is exacerbated by moving dark areas such as a dark background in a video, or scrolling a website with a black area etc. My own findings have been:

Things that has no effect:

• • The connection method - HDMI, USB-C to DP or USB-C to HDMI - flickering happens with them all
  • Quality of cable - have tried a variety of cables and USB-C adapters, they all have the issue
  • Big Sur version - i'm not sure what the M1 Mac came with when I bought it, but i've kept it up to date and had the flickering on all versions, including on the recent 11.3
  • Display scaling settings - no difference between them

Things that reduce the flickering but don't eliminate it completely:

• • Accessibility options -> Display -> Display contrast - increasing this reduces how often the flickering happens
  • Monitor colour profile - changing this from Dell S3221QS to sRGB had a drastic reduction in flickering, but it hasn't solved it completely.

Oddly enough though, my Macbook Pro 15" 2015 also exhibits the exact same flickering problem on this monitor over HDMI which leads me to think this is a software problem in conjuction with certain monitors, and not an M1 specific problem.

The monitor itself is absolutely fine when using it with Windows 10, I've tried my best to replicate the same colour scheme and conditions but I just cannot get the problem to occur on Windows, so the monitor is unlikely to be the problem here.

I also have a Dell U3415W Ultrawide monitor, and I do not get any flickering with this monitor at all.

Hopefully this can be resolved at some point as it's rather offputting, especially full screen videos and games where the problem is extremely noticable.

My wife bought a new Mac Mini M1 and we got a ASUS 28 inch 4K monitor and ran into flickering issues using the HDMI cable. I did some more searching around the community and found that some people had success by going to System Preferences -> Display -> Hold Option key when clicking on the "Scaled" radio button. Make sure to then check the "Show Low Resolution Modes"

This should allow you to set the refresh rate. I choose an appropriate resolution and hard set the refresh rate; happened to be 60hz for this monitor.

Sadly it didn't completely solve the issue, what did though, was a combination of the above and getting a USB-C to DisplayPort cable. Since then no flickering has been reported by my wife.

I have a similar issue. I get flickering on the internal screen of my M1 MBP running MacOS 11.1. I use a Dell U3818DW ultra wide 38" https://www.amazon.com/gp/product/B073FHWTPL/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1 via a DisplayPort to USB-C style cable that came with the monitor.

I have never noticed flickering on the Dell monitor, only the internal one.

The flickering goes away when I uncheck "Automatically adjust brightness" in the display settings. I do not have to change my refresh rate.

When I re-check the box. I get intermittent intense flickering.

Hope they can fix this in a future release.

Hope this helps others!

I have exactly the same problem, only I switched from the LG 27UL500-w IPS monitor to the DELL S3221QS with VA panel. For a long time I could not understand the reason for these vertical stripes. I changed a bunch of cables and realized that my MacBook Air M1 just doesn't work properly with monitors with VA panels, but I found that on/off NightShift helps for a while. Apple should fix this problem. I hope...

The Dell S2817Q is an IPS display and has the issue on my M1 mini. I bit the bullet and ordered a display others have posted about using successfully with the M1 macs — the LG 27UK850-W — and it’s working via Thunderbolt and HDMI with no hiccups whatsoever. At least i know for sure that it’s monitor-to-monitor, not something about the particular Mini I received that chokes when ANY 4K display is attached.

Just found the following article, looks like this issue is getting even more exposure now:

https://piunikaweb.com/2021/01/08/apple-investigating-mac-mini-m1-external-display-flickering-issue-on-dark-backgrounds-no-release-date-for-fix/#:~:text=Apparently%20known%20issue%20of%20M1,upon%20by%20their%20engineering%20team.

I'm having the same issue. I also bought a USB-C - DP cable. While it solves this particular issue (grey vertical lines and sometimes ghosting if left unchecked), it also creates a new one. Sometimes, after waking up the Mini from sleep, the monitor is showing pink lines in the upper part of the screen. I need to turn it off and on again to get it to work. Still, it's much better than the issues I've been having via HDMI and USB-HDMI cables.

What's most annoying, is that I had literally zero issues in the past, and I've been using my monitor with a Windows laptop, PS5, Series X and now the Mini. For all other devices except the Mini it works flawlessly, so I am seriously disappointed how Apple is handling things here.

I regret not returning the Mini while I still had the chance. I didn't do it because it felt like an obvious quick kill on Apple's side, especially considering how impactful this is and how many people report issues with external displays.

Hey guys, I don't have the same exact monitor as you guys, but I'll give you a background on my issue:

Flickering was constantly happening, like every hour, triggered usually by web browsing pages with many images/videos.

This almost completely stopped after I used the second HDMI input on my monitor as well as switching cables (using a short 3ft braided cable), but not completely, at this point it didn't happen randomly, only on certain webpages.

So I did some testing and the web pages that I went to that triggered the issue at will no longer did after I changed my scaling settings by going into system preferences, Displays, and 'Option'+Clicking on scaled, and I set the scaled resolution to 2048x1152 (If the issue is only happening with web browsing certain pages for you, then changing the zoom on those pages to 90% also stopped the flickering for me, but considering I've heard the issue happens outside of web browsers, I believe changing the OS scaling setting to be the more permanent fix). Sure things look a tiny bit smaller now, but I have been flicker free for a couple of weeks now. You guys can give it a shot and see if it fixes it. Before anything, make sure you are using short (preferably 3ft or less) certified HDMI cables or else I can assure you, your problem won't be solved. Also, don't assume your HDMI cables are good like I did (they may be literally good for everything else except the M1 Macs.) FYI, I'm using a 3ft Zeskit Maya HDMI 2.1 (8K) cable (overkill for my monitor but it's doing the job).

Hello, I believe I have found a "fix", it's more like a workaround. This issue happens because the m1 defaults its video output to ypbpr, instead of RGB. You can edit the com.apple.windowserver.displays.plist file to force RGB output. This will fix the problem of vertical lines, image retention and flickering.

This video explains it really well https://youtu.be/Z1EqH3fd0V4

Got the same issue with BenQ (see my post and report here: https://discussions.apple.com/thread/252831568). My local AASP diagnosed it and it needs main logic board replacement! Woohooo! I've only used the mac mini M1 for barely a month.

I have a M1 Mac mini bought July 2021, and a Asus VP28U monitor and have started experiencing the vertical lines, particularly noticeable in dark mode. I can readily replicate the problem just opening a PNG file in Quicklook - sound like it's different conditions for different people. Switching out the HDMI cable did not resolve the issue (tried about 4 cables of various qualities). Fortunately the Asus also has DisplayPort input so I bought a Comsol USB3 to DP cable and hooked it up. The Mac happily serves up 4k@60hz and all the lines, flicker and ghosting is gone. For me I'm pointing my finger at something dodgy going on in the HDMI implementation. Hopefully new firmware or OS will fix it up one day, but having a DisplayPort alternative has me solved for today.