Disabling Adaptive Brightness in Windows 8 or 10
Hit the Windows key, and then type in “Power Options” into the search, which will pull up the Power Options panel.
Once here, click the “Change plan settings” link on the selected plan.
Then click the “Change advanced power settings” link.
And now, browse down to Display –> Enable adaptive brightness, and change the settings there to Off.
Changing this setting fixed my brightness problems on my MacBook Air running Windows through Boot Camp.
