From what I have read early on was that 4k is upscaled 2160p and cropped in-camera, this was made from the conclusion that it lacks sharpness and had more aliasing than UHD.  Whether this really is the case is debatable because I have no idea how it really works, it could be true line skipping for all I know.  When I shoot 2160p or 4k in NX500 I get fine noise grain like in 1440p mode, its just smaller grain which is expected duo to higher resolution. Why is this? I use Kino's Mod Pack