Per Dell-Cares:  This system is working as designed. After Windows build 20H2, adaptive brightness is now controlled by the OS. With that said, the settings below can help and be used as a workaround in some cases:  For this system - entering the BIOS and turning off Eco Mode will disable adaptive brightness in the OS (this was the solution for this system).   Note On some systems, using the Intel Graphics Command Center can also sometimes disable it (not the case with this model). IGCC can be found here.
My laptop is a Dell Inspiron 5510 with an i7 processor and Intel Iris Xe Graphics. My problem is that the computer automatically adjusts the screen brightness based on what images are being displayed on the screen. (This happens only when the laptop is running on battery when it's plugged in there's no problem) For instance, when I open up a word document the screen becomes very bright because of the white background it is displaying but when the screen displays a darker image like a webpage with a black background the screen brightness noticeably dims. At first, I just assumed this was some graphics or power-saving setting. Is there some well-hidden setting causing this, is my laptop screen defective, or is this just the way the laptop is? I need to know. It's driving me nuts. ( I don't see an option of adaptive brightness in advanced power settings>>display)
Inspiron 5510, Dell Adaptive Brightness