What can I do if I can't adjust the brightness of the screen after upgrading win10?

Problem Analysis:
Win10 system screen can not be adjusted The problem is mainly caused by the modification of the registry, we can modify the settings by changing the registry value data. It is important to note that it is best to back up before modifying the registry to avoid unnecessary trouble.
Workaround:
1, use the shortcut key in win10 "Win+R"; open the run window and enter "ldedit" rdedit; press OK to bring up the registry editor.

2, search for the "featuretestcontrol" option in the registry.

3. After finding the featuretestcontrol option, modify its numerical data to ffff, and finally click OK to restart the computer.