NVIDIA auto-contrast on battery issue (Precision M4700 / M6700 / M4800 / M6800 / 7510 / 7710)

I barked up the NVIDIA tree as far as I could and finally got a response from someone who seems to be, at the very least, not completely clueless.

He says that the cause of this contrast shift / dimming is a power saving feature called "SmartDimmer". They also pointed me back to Dell to get anything fixed.

I guess the implementation in my affected systems (all using LG displays, I believe) is not so great, making the effect particularly annoying. I found this old NVIDIA article that describes the feature. Working to see if it is possible to disable, now that I know what it is called.

 

I'm fairly sure the IGZO screen I have is a sharp and not LG.


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Is the goal to find a way of disabling Nvidia PowerMizer or to disable just SmartDimmer which is a feature of PowerMizer?

btw, the 4k display in my 7710 is an AUO109B.

 

I would prefer to just disable SmartDimmer, but would possibly settle for disabling PowerMizer if it also disables SmartDimmer (or whatever behavior we are actually observing), if that doesn't impact battery life too adversely.

I found some references to relevant registry values in the NVIDIA driver INF file (i.e. "EnableBrightnessControl", "SmartDimmerEnable", "NvCplDisableSmartDimmerPage") but haven't had any luck with them yet, they seem to be not present on my system or do nothing if I change them.

 

That's a cop-out; it's their feature, not Dell's, and should be made optional in nvidia's driver.

Anyway, the Technical Brief of PowerMizer 8.0 shows it ought to be possible to disable it in Power Options (at least in Vista and Windows 7, apparently). Since you've already tried that to no effect, perhaps with 8/10 it has been renamed or the guid has changed and made a hidden option. There's tons of those and not all have a 'FriendlyName' value. The hide switch is a Dword 'Attributes' with value 0 or 1:

Spoiler: hidden Power Options

Could search for 'Attributes' starting at 'HKLM\SYSTEM\CurrentControlSet\Control\Power\PowerSettings' and replace every instance with '1' for '0'. Made a lazy spreadsheet on Sheets to make this a bit less tedious and also to have access to it while tinkering with other people's machines. Restart or log-off isn't necessary; re-open Power Options and the previously hidden values should show up. Hopefully that SmartDimmer abomination is still there, but if it isn't then it's up to nvidia to fix their installer to make sure it's there and functioning, as any non-critical feature should be.

 

Yeah, I've been through the power options stuff already. The relevant option is hidden by default, but even making it available in the GUI (which you can do in the registry), you can change it but the changes don't actually do anything. I went through every GUID in HKLM\SYSTEM\CurrentControlSet\Control\Power\PowerSettings, no luck. I've also run Sysinternals Process Monitor to observe which registry entries are read when the power state changes and nothing came out of that.

Also tonight I dug up some old threads on different forums for disabling SmartDimmer/PowerMizer, everything I can find seems to be from around 2009-2011, and none of it has worked.

 

having recent hexing of my m6500 to boot into a bsod over the weekend --- I was trying to get aggresive uninstalling garbage programs in regedit, I'm happy to let you guys experiment.

*off topic: Good news is that after a fresh OS install, my m6500 is faster than it was before the blue screen. It was 6+ yrs of trash accumulating on that laptop. Fresh install fixed it right up.

Thanks for taking charge Aaron

 

Unfortunately, with no solution, I'm mostly out of ideas. :-\
I'll write back to Dell tomorrow with NVIDIA's information.

Here are some references to other threads I have found about disabling PowerMizer and SmartDimmer.
PowerMizer - http://forum.notebookreview.com/threads/disable-powermizer-tested.261929/
SmartDimmer - http://forums.laptopvideo2go.com/topic/20133-help-to-disable-smartdimmer/
There are others but none are very current and they all point to mostly the same registry values.

I messed with these registry values but was unable to get any change in behavior regarding these issues.
PerfLevelSrc
SmartDimmerEnable
EnableBrightnessControl
PowerMizerEnable
PowerMizerDefault
PowerMizerLevel

None of these were actually present on my system but they are all referenced in the NVIDIA driver INF and most of them are also referenced in the nvlddmkm.sys file, so I was able to figure out where they "should" go.


I think the main reason that not many people are complaining about this, despite it being a pretty easy issue to reproduce, is that it doesn't show up with Optimus/graphics switching enabled and that is the default state for these machines, so it is rarely noticed. Oh and also most other current-generation laptops with dGPUs come with graphics switching and no way to turn it off (even some high-end ones like Dell's Alienware line), so you would never run into this anyway.

 

Found a fix.
I'm going to have to look into the downsides of doing this, but disabling the "ACPI-Compliant Control Method Battery" in Device Manager prevents the NVIDIA driver from noticing the power state change. You can still run on battery, and the auto-contrast issue goes away.

An obvious problem is, you can no longer tell what the remaining battery level is... The icon disappears from the system tray and nothing in the system seems to be able to tell that the battery is present.

 

Still looking for a "proper" fix, I started looking at the strings in nvlddmkm.sys again and ran across a few that I had not noticed before...

enableDarkSceneBLReduction
DarkSceneBLReductionLuminanceLevel
DarkSceneBLReductionThreshold
DarkSceneBLReductionBrightnessLevel
DarkSceneBLReductionPixelGain

These appear to be for registry settings that are directly related to this problem, described as "dark scene backlight reduction". They appear to be unknown to the Internet (Google search for the specific strings returns nothing). I haven't been able to figure out what they do or how to set them properly, if it turns out that they are even related, but I'm going to engage with NVIDIA again and see if they will tell me anything.