If you’re like me, I do not want my screen to change brightness, especially if the light level of the room is changing frequently, causing the display to change just as frequently. Some hardware may have the ability to disable this functionality, but I will show you how to turn it off in Windows 8 and Windows 8.1. This should also be similar for Windows 10, though I haven’t tried it yet.
1. Click on Start 
and type Power Options
2. Click on Power Options
3. Next to your currently selected power plan, click Change Plan Settings
4. In the Edit Plan Settings window, locate and click on Change advanced power settings
5. Locate and Expand Display > Enable Adaptive Brightness
Note: You may need to click Change settings that are currently unavailable to make changes if you are using UAC (User Account Control)
6. Choose either On or Off, depending on the setting you would like to have. For mine, I have it turned on while using battery power, but turned off when connected to the wall.
7. Click Apply and OK to save the changes and close all windows.
If you decide you want to turn this feature on again, just follow the instructions to change the option later. You will also need to change this option for each plan if you use different plans regularly. I do not mind the loss of battery life, so my laptop always runs on the “High performance” plan.
