I just looked at the resolution numbers and its clear what the issue is.. Its a 3MP camera which works at 2048x1536 and this is 4:3, not 16:9..
But the odd thing is, Hikvision could "crop" a 1920x1080 image out of this 4:3 frame and make a 2MB 16:9 image, so its odd they havn't done this...
So...