By default most 1080p TVs are not set up correctly to display a 1080p source right out of the box. This is very common on Samsung and Sony TVs, but probably on others as well. I am more familiar with Samsung models so I will walk through how to change the settings in your menu on it to get a real 1080p image on the television, but it is very similar for other TV models. Without making this small change your TV is displaying a resolution more along the lines of 950p.

On a Samsung 1080p model change to your input that has the 1080p source on it and go into the TV's main menu. From there select the picture option. Scroll down until you get to size and it will be defaulted to the 16:9 option. This needs to be changed to Just Scan (its called something different for each brand, on Sony sets it is called Full Pixel). If you swap back and forth you will be able to see the screen expand, because the 16:9 setting slightly zooms in a 1080p signal.

Hope this helps out any CAGs that might not have know about it.