I have been using blender for about a year now and have only just started to notice that all my pictures are actually not that HD. If you zoom in on a render just once, you can see each individual pixel colour. I don't know if this this is a big or if it is something I can do or even if this happens to everyone. Please help as its really bugging me now.
Here is an example of a render that is a bit pixelated:
Save the picture and open it in fullscreen and zoom in just a bit.