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Eye-Burning Bug in macOS Catalina on 2019 Mac Pro: LG 5K Display Resets to Maximum Brightness Every Reboot

Update: it gets WORSE; see Caution for Those Working with Color-Calibrated Displays.

There are so many bugs in Catalina that I could spend weeks writing them up.

Here’s one that is not just eye-popping (literally), but of great annoyance to me as a photographer—I need the display to remain stable and predictable.

After every reboot, the LG 5K display goes to maximum brightness.

Update: the Apple Pro Display XDR shows the same behavior as the LG 5K—max brightness after reboot. At least it is consistent programming incompetence.

For all I know it is not specific to the Mac Pro or Catalina either, but I don’t intend to test in other situations.

After reboot, Brightness of LG 5K display is set to maximum after reboot
After reboot, Brightness of Apple Pro Display XDR is set to maximum after reboot

Erik K writes:

We had this same exact issue with an iMac Pro when they were first released.

Bought 2 machines and one of them was useless to us with this issue.

After a long time with Apple support, they said it was a known issue but there was no solution at the time. Eventually I was able to convince them to take the machine back if I ordered another and it was problem free. Ordered another, it was fine and they took the problem one back.

Sorry to see the issue is still around.

MPG: I was getting eyestrain today, working intensely, until I realized it was caused by the brightness on the LG 5K being cranked all the way to maximum again. Apple Core Rot.

Stephen S writes:

I took delivery of a 16” build to order MacBook Pro 4 days ago. It’s going back tomorrow due to this bug. Luckily, I’m within the 14 day no questions asked return period, so the return will be hassle free. Yah, I spoke with Apple support and they don’t have a solution. Could be hardware. Could be software. Could be a confluence of both (that’s my best guess after seeing same symptoms on a Catalina 15” unit but only on rare occasions where I plug or unplug external displays. So…. Thank you for publishing your note. It gave me the confidence to speak to Apple and refer to other people experiencing the same issues (there are discussions online as well). So unfortunately I won’t have a new laptop for my upcoming trip.

...when the computer is connected to the LG 5K the internal display will frequently set itself to 100% brightness. Not 100% of the time, but frequently enough on restart or startup from being off.

I tested the 16” MacBook Pro and LG 5K Ultrafine. I’ve had the Ultrafine since 2017 used with a 2016 15” MacBook Pro. No display issues up to and including Mojave. Observed behaviours: On reboot, sometimes both the built in and the LG jump to 100% brightness. Sometimes only the built in. It does *not* do this on every reboot. It’s frequent, but unpredictable. I haven’t noticed a pattern yet. Maybe there is one, dunno.

Sometimes brightness jumps when waking from sleep (not just restart or shutdown/restart) on one or both monitors. On occasion, the screen reboots at 100% and resets itself to a proper brightness when the OS X log on screen on the LG is passed. Weird. Rare. Seen twice. My best guess is that there is an interplay between stuff in Catalina and how it plays out on different model Macs. As a control, I upgraded my old 2016 15” MacBook Pro to Catalina.

The 2016 15” MacBook Pro has never reset brightness through reboots, shutdowns and wake from sleep during dozens of tests the last two days, or 3 years of use prior. However, If I unplug or plug in the LG or otherwise change things up it DOES shoot the built in display to 100% now that Catalina 10.15.2 is running on it. So, I’m thinking Catalina is a factor in this new behaviour on old hardware. Duh.

My best guess at what’s going on: I think it’s related to Catalina, but severity may depend on different variables that are hard or impossible to know (ie: what hardware it’s being run on, or even if there is a flaw or out of tolerance with hardware somewhere. Thus, on the 16” this behaviour is exacerbated, happening very frequently (I searched Internet forms and this has been reported since November) - but form postings are anecdotal and I give small credit to them. Which is why I was glad to see your blog post.

My plan: I think a software upgrade could fix this, but since the ownership experience sucks and I can return it without penalty (within 14 days of purchase) that’s just what I’m going to do. I can’t justify the cost of a 2019 Mac Pro. And I would like a decent preforming laptop for travel.

Last thing. Unless there was something like a non-spec hardware part supplied during build out, it amazes me that Apple did not test this issue. The MacBook Pro with an LG 5K Ultrafine - no other third party hardware. Not even a cable. And they sell them both. Geez. It pisses me off that NONE of the reviewers, idiot YouTube Apple Surrogates or anyone jumped on this.

But, then again, I’m assuming the issue is universal or widespread. It may not be. Last, but not least, based upon the suggestion from a level 2 Apple Support rep, I created a new volume in my APS container and used recovery mode to re-install macOS Catalina. I skipped all customizations during first time setup. So essentially I had a brand new out of the box Mac with no configuration except Administrator Account name and password and it still didn’t work properly - after booting the screen brightness on both monitors was 100%!!! It’s up to Apple to fix this. Not me. I spent over $6,000 Canadian and over 20 hours of config and trouble shooting :)

Show stopper? - a qualified yes. It takes about 15 seconds per screen to reset brightness using a screen shot with the proper slider displayed for reference. So it’s a hassle especially if it happens many times per day - but it’s not critical to my work. I still have my NEC for colour correction which is unaffected by the bug in Catalina. But it’s annoying as hell after spending $6K.

Here’s my qualification: The computer was ordered Jan 7, arrived Jan 14. I have until Jan 29 to return it “no questions asked” as part of Apple’s Sales policy, not their Service policy. It’s much harder to get a replacement through Apple Service later. They have to make the determination to replace it, not me :) Since I am able to get a full refund until Jan 29 then yes, why would I suffer through such a defect with no known resolution? So I’m lucky in that way. I’ll wait a few more weeks to see if there is a Catalina update which “fixes” this. I don’t need the better computer urgently. Maybe Apple will release newer versions of the smaller MacBook Pro that would be tempting? Maybe an updated iMac Pro? (Which likely won’t be my choice anyways). I hope all that made sense!

MPG: witness the colossal waste of customer time and effort (“20 hours”)—Apple manure-grade quality control has also cost me dearly in the past few years.

The Apple Pro Display XDR features extreme brightness capability. It could be very unpleasant and a serious professional work problem if it just goes changing the calibrated/chosen brightness and resetting the display profile. The stink of Apple Core Rot gets ever stronger.

Of amusement to me is a premise I see all the time, reflected in “NONE of the reviewers, idiot YouTube Apple Surrogates or anyone jumped on this”. The fact is whether it is cameras or computers or cars, 90% of “reviewers” are incompetent at basic observation and 99% want the next thing to review, and thus will not spend a word on ‘minor’ issues. That’s the way the game works, and it’s why very few companies loan me gear for review—cheerleader reviews for large gullible audiences are the ticket (in other words, a process of pure unadulterated marketing masquerading as reviews). There is little integrity in the review process, and once you understand that, you’ve understood the world a lot better, and there should be amazement in the other direction—seeing issues pointed out.

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