Oh no ... really? It's happening on this monitor too? I have the Dell 2740L as well which has this issue and I thought it wouldn't happen to this model. It's really bad on the 2740L, and Dobr and nokey (another post thread) captured the exact way it shows up in photos on the U2413.
I wanted to upgrade my graphic card driver - so I've downloaded the new version from dell official web site. I got the error that it's not compatible.. I read somewhere that it's good to uninstall the previous driver and to install the new one.