I have an Optimus Elite, and it has a minimum brightness setting. In certain apps, I can reduce the brightness below the safe minimum, but when I leave the app, the brightness is increased to the system-wide minimum.

Using RootDim, I can permanently set the brightness below the safe amount, and it will stay even after going to other apps. Or using Screen Filter, I can accomplish almost the same thing even without needing root (it displays a translucent 'filter' over the whole screen, reducing brightness/contrast but not actually changing the backlighting power amount).

What I want to know is where the minimum screen brightness is stored. I have a rooted phone with CyanogenMod 9, so I have permissions to edit anything and could change a config or sqlite entry, but I don't know where this value is stored. What I would like to do is use the status bar brightness slider to be able to slide to the actual minimum of the screen, rather than the OS-controlled minimum. Having an app is useful, but having the functionality without the app seems to be within reach, if only I knew where the OS is getting it's safe minimum setting.

Where is this "safe minimum brightness" setting stored? If I can change it, I can remove my apps and use native controls.

4 Answers 4


Editing /system/build.prop and changing the ro.lcd_min_brightness property may work. That property may not exist in your file (It doesn't in the file for my GS3), in which case it will default to 20. Lower numbers mean lower brightness.

This doesn't actually work on all devices though. For example, on the Galaxy S2, setting the property to a lower number will allow you to set the brightness control lower, but the actual screen brightness won't go any lower than it did before.

Alternatively, Cyanogenmod includes controls to customize the auto-brightness levels under settings > cyanogenmod settings > display > automatic backlight. There's an explanation of how to use the custom configuration over here at rootzwiki.

  • But is there a way to make it dimmer than cyanogenmod's dimmest?
    – endolith
    Nov 28, 2014 at 17:04

Super late, I know, but this may help out anyone who comes across this later. What I did for my phone, the Alcatel Fierce, I got ES File Explorer and browsed until I found the LED controls. For my phone its in /sys/class/LEDs/LCD backlight/ then there is a file named brightness which controls the actual brightness of the phone. I viewed it as text and saw on the lowest setting it says the brightness is 30 so I changed it to 10 and saved and automatically the brightness dropped to a much more suitable level.

Note. For all devices and ROMs this may not be the same but just use the search to find brightness, LCD, or backlight. Be careful when changing values and be sure to remember what they were if you don't have custom recovery!

  • Is there such a file for the minimum system brightness? This one works great to set current brightness but the minimum isn't changed...
    – Matthieu
    Jun 19, 2019 at 13:50

Give Lux Auto Brightness a try. I used to use Screen Filter for reading but I like the way Lux does it better.

Edit: My bad, you said without an app. I don't know of any way to do it without an app. Still give Lux a try it might work for you.

  • 1
    Even if I needed a different app, apparently Lux is incompatible with all my devices. How strange; I have several Android versions and form factors, and I haven't seen an app before that was incompatible with all of them.
    – Stephen S
    Apr 23, 2013 at 14:47

Try Wellbrightness.

It will enable screen filter when you need darker than minimum limitation.. And it's very simple and intuitive...

  • 8
    That kinda fails the "without an app" requirement.
    – ale
    Aug 21, 2013 at 2:59

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