Distortion in your picture quality is more than likely a side effect of non-HD devices being attached, or by easily-changed settings in your television menu. Changing your settings and making sure that you have the right hardware can help ensure the best possible picture.
Low Quality Devices
Watching standard cable on an HDTV can be quite a shock; the images are likely to be in a smaller aspect ratio, and have grainy or pixelated distortions. Additionally, the use of non-HD compatible devices, such as a DVD player, VCR, or older gaming system, will produce a less than stellar picture.
Video of the Day
If you've changed the aspect ratio or your television, or have changed the zoom in or out, you may be encountering distortion that would otherwise not be noticeable. Setting the picture to a 1:1 ratio and turning off any overscan can help ensure a better quality image.
If you're using a system that supports HD, such as a Blu-ray player or an HD-compliant gaming system without the use of an HDMI cable, the image may be distorted. HDMI cables transmit both HD quality digital images and sound over one cable, and provide the best possible picture A/V signals.