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mzanker

macrumors 6502
Original poster
Jul 14, 2008
307
111
United Kingdom
Every few days auto-brightness stops working on my base model iMac Pro. It appears to happen when the display has been off for a while (I've disabled sleep when the display is off). It appears to get stuck in the dimmest setting.

Unchecking/checking the "Automatically adjust brightness" setting doesn't fix it - a restart is needed, which fixes it every time (until it happens again).

I'm hoping this is a software or firmware issue (or even a driver issue) and not a hardware fault. Anybody else had this happen?
 

mzanker

macrumors 6502
Original poster
Jul 14, 2008
307
111
United Kingdom
I decided to start uninstalling hardware-related utilities to see if anything made a difference. The first thing I uninstalled was iStat Menus 6 and I haven't had the auto-brightness issue since.
 
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daveives

macrumors newbie
Mar 30, 2018
4
0
Every few days auto-brightness stops working on my base model iMac Pro. It appears to happen when the display has been off for a while (I've disabled sleep when the display is off). It appears to get stuck in the dimmest setting.

Unchecking/checking the "Automatically adjust brightness" setting doesn't fix it - a restart is needed, which fixes it every time (until it happens again).

I'm hoping this is a software or firmware issue (or even a driver issue) and not a hardware fault. Anybody else had this happen?
[doublepost=1522435768][/doublepost]My iMac PRO base model is dimming precisely as described above. I have no idea as to. what to do.
 

boto

macrumors 6502
Jun 4, 2012
437
28
I think I'm experiencing something similar. I noticed after updating to 10.13.4 my screen brightness is set 2 bars away from max and needs to be manually readjusted after a restart/shutdown. I tried SMC/NVRAM resets, reinstalling High Sierra, deleting system preference and ambient plists, and nothing seems to work. Is anyone else experiencing this after updating or can anyone offer some suggestions to force screen brightness to lock and save?
 

Mac32

Suspended
Nov 20, 2010
1,263
454
I think I'm experiencing something similar. I noticed after updating to 10.13.4 my screen brightness is set 2 bars away from max and needs to be manually readjusted after a restart/shutdown. I tried SMC/NVRAM resets, reinstalling High Sierra, deleting system preference and ambient plists, and nothing seems to work. Is anyone else experiencing this after updating or can anyone offer some suggestions to force screen brightness to lock and save?
I have the same thing after the 10.13.4 update (iMac Pro 8c/Vega64/32gb). Apple's QC has really slipped the last year.
 
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Strider64

macrumors 65816
Dec 1, 2015
1,443
12,293
Suburb of Detroit
Hmm I didn't realize the iMac Pro had this feature built-in, for my X-Rite Spectrometer I use for calibrating my monitors has that feature as well. Learn something new everyday.
 

Bryan Bowler

macrumors 601
Sep 27, 2008
4,025
4,353
I have the same thing after the 10.13.4 update (iMac Pro 8c/Vega64/32gb). Apple's QC has really slipped the last year.

Every single MacOS update introduces more problems and things that slow me down. First they bricked Duet, now this, and who knows what will surface next.

At the end of the High Sierra cycle, no more OS updates for me until April/May of 2019. I have work to do and Apple’s lack of software QA is costing me money.
 

EDS66

macrumors regular
Mar 31, 2018
118
115
I think I'm experiencing something similar. I noticed after updating to 10.13.4 my screen brightness is set 2 bars away from max and needs to be manually readjusted after a restart/shutdown. I tried SMC/NVRAM resets, reinstalling High Sierra, deleting system preference and ambient plists, and nothing seems to work. Is anyone else experiencing this after updating or can anyone offer some suggestions to force screen brightness to lock and save?

I have exactly the same issue. iMac Pro 8 core. Brightness resets to about 90 percent after each restart (2 bars from maximum.) Did PRAM reset and SMC reset (several times). No effect.
 
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mossback

macrumors member
Nov 18, 2007
96
106
PNW
I have exactly the same issue. iMac Pro 8 core. Brightness resets to about 90 percent after each restart (2 bars from maximum.) Did PRAM reset and SMC reset (several times). No effect.

Identical problem.
 

EDS66

macrumors regular
Mar 31, 2018
118
115
Identical problem.

This issue popped up on apple discussions forums yesterday as well:

https://discussions.apple.com/thread/8341298

I reported this to apple; hopefully others will as well. I don't think Apple bundled a firmware update for iMac Pro with 10.13.4. My guess is it's a kext issue. Unfortunately apple releases fixes at a tectonic pace, and we will probably have to live with this problem until the next High Sierra update.
 

floridaman

macrumors member
Nov 8, 2011
93
35
Florida
Something else I noticed with brightness is when night shift is on and you adjust brightness up to the second to last bar and then advance to last bar there is no change in the brightness. When night shift is off the brightness adjustment works correctly, adjust from second to last bar to full brightness and you can see the screen get brighter. Very strange. By the way the auto brightness on my IMac Pro behaves differently than what is being described in this post. Mine adjusts to almost full brightness when there is bright sunlight in the office, however as the sun goes down my screen brightness drops down to 3-4 bars which is too dim. When I turn on bright lights in the office the brightness might go up 2 bars at the most. I am running 10.13.4. Apple needs to spend a lot more time doing testing before releasing these updates especially with these flagship models.
 
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EDS66

macrumors regular
Mar 31, 2018
118
115

I don't think there is much you can do, other than reporting this to Apple. One of the contributors in the apple support forums I referenced above reported that Apple Engineering is looking at it and that he has another call scheduled on Thursday. Hopefully, if enough iMac Pro owners report this problem, Apple will release a fix in short order. But given their track record, we will probably have to wait until the next High Sierra update.
 

daveives

macrumors newbie
Mar 30, 2018
4
0
I disabled "Adjust keyboard brightness in low light" under the "Keyboard" Panel under "System Preferences" and the screen dimming seems to be fixed. Perhaps this control gets sent to the display screen instead of the keyboard.
 

mzanker

macrumors 6502
Original poster
Jul 14, 2008
307
111
United Kingdom
I disabled "Adjust keyboard brightness in low light" under the "Keyboard" Panel under "System Preferences" and the screen dimming seems to be fixed. Perhaps this control gets sent to the display screen instead of the keyboard.
Which keyboard are you using? I don't appear to have that option (using space grey bluetooth keyboard).
 

daveives

macrumors newbie
Mar 30, 2018
4
0
I disabled "Adjust keyboard brightness in low light" under the "Keyboard" Panel under "System Preferences" and the screen dimming seems to be fixed. Perhaps this control gets sent to the display screen instead of the keyboard.
system 10.13.3 1 month old space grey (like black silicone)
 

EDS66

macrumors regular
Mar 31, 2018
118
115
So, I reverted to 10.13.3 (from recovery) and the iMac Pro still does not remember the brightness level on restart. Must be a firmware issue.
 
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alkar

macrumors regular
Jan 12, 2008
166
22
firmware got updated with 10.3.4 so it's possible. Did you try to reset SMC/NVRAM ?
 

EDS66

macrumors regular
Mar 31, 2018
118
115
Apparently this problem predates 10.13.4, at least according to the support call one of the members of Apple Support forums had with Apple Support. I reverted to 10.13.3 and the issue persists. It's quite possible I simply never noticed it before.
 

mossback

macrumors member
Nov 18, 2007
96
106
PNW
In my case, the issue was not present in 10.3.4

Perhaps reverting does not alter the parameters in question?
 

EDS66

macrumors regular
Mar 31, 2018
118
115
In my case, the issue was not present in 10.3.4

Perhaps reverting does not alter the parameters in question?

If the firmware update did it, then reverting to a pre 10.13.4 build would definitely not help things. SMC and PRAM resets are not effective, by the way. I've tried both several times after downgrading to 10.13.3.

The problem does not bother me too much, as I rarely restart the computer and never use automatic brightness adjustment -- don't really see much utility in it.

Let's hold our fingers crossed and hope Apple releases a fix -- either software or firmware -- without too much procrastination.
 

mossback

macrumors member
Nov 18, 2007
96
106
PNW
My apologies! I meant to say 10.3.3 in the above post.

To clarify, I'm running 10.3.4 currently and the issue is present. But it was not with 10.3.3
 

EDS66

macrumors regular
Mar 31, 2018
118
115
If the firmware update did it, then reverting to a pre 10.13.4 build would definitely not help things. SMC and PRAM resets are not effective, by the way. I've tried both several times after downgrading to 10.13.3.

The problem does not bother me too much, as I rarely restart the computer and never use automatic brightness adjustment -- don't really see much utility in it.

Let's hold our fingers crossed and hope Apple releases a fix -- either software or firmware -- without too much procrastination.
My apologies! I meant to say 10.3.3 in the above post.

To clarify, I'm running 10.3.4 currently and the issue is present. But it was not with 10.3.3

You mean 10.13.3
 
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