APEX LE40H88 not sharp picture when connecting pc through HDMI

I got the APEX LE40H88 tv. Recently I decided to connect the pc through the HDMI cable. My pc got the ATI HD6670 video card.
But the picture on the tv appears to be not sharp and not smooth. It looks like distorted. The picture on the monitor is perfect.
I tried to play with the video card settings but did not get any result. I remember having the same problem with my SAMSUNG tv.
In case of SAMSUNG the only thing I had to do to get the perfect picture on the tv was to assign the proper name to the HDMI channel on the tv itself (it was like setting up the proper preset profile on the tv itself).
But on the APEX tv there is no such thing or I could not find one and there is nothing in the manual.
Any suggestions would be appreciated.

Thank you.

The PC and TV native resolution is 1080p. The scaling option is 0% and the TV is set to 1:1.

Actually the scaling is not set to 0% it is set to default, which is smth in the middle. But the thing is that changing the scaling option does not change the picture sharpness or smoothness, just its size.