Make sure HDR is turned off in Windows. Make sure no ambient light sensor adjustment is selected.  
For some reason in my AW3821DW settings, the Brightness is greyed out. I can adjust the Contrast, just not the Brightness and I wonder why that is? Am I the only one who has this problem? I do like to adjust these settings myself and would really like to know if there is something that can be done to unlock the Brightness setting on the AW3821DW?
AW3821DW, Brightness setting greyed out