Bought a new T490, extracted all of it's OEM drivers as I had to reimage it to W10 Enterprise for BitLocker support (required by my University). After reinstalling all of it's OEM drivers, I have no control of brightness. I tried disabling and reenabling the graphics driver in Device Manager. In power plan options, there is no brightness slider, and the FN designations for brightness control do not work (the other FN functions do work!). I think it's a driver issue, the laptop has a NVIDIA MX250 2GB, and I tried both the OEM driver and the driver from the NVIDIA website with no luck. Downloaded the monitor .ini file from lenovo and installed that over the Windows 10 OEM monitor driver, no dice as well.