The most resolution of the DT-E21L4U is 480i. That's 56% less resolution than the most frequently found video mode of 1080p (which is also found on this flatpanel monitor). This PC monitor also have 1080i, 480p, 576i and 576p and 720p video modes.
This PC monitor's resolution (480i) is in fact the worst resolution amongst all medium monitors that were launched around the same time as the DT-E21L4U.
The best resolution across similar types of PC monitor is 1440p.