I don't have a PC that can play DKS at an acceptable performance, so have not tried PrintScreen or any screenshot programs (many rely on the standard PrintScreen function) with it (or any other recent game).
What is wrong with the graphics? Do you mean 'smooth' as in anti-aliasing?
DKS does not support hardware MSAA (see
here for details), but people have gotten AA working. Originally some people had success disabling HDR lighting or renaming the executable to get their video card drivers to use the settings for another game, but there should be better methods now.
Anti Aliasing: Simple and effective solution foundThe drop in resolution for the YouTube videos may have helped them look a little better.