What is the difference between 720p and 1080p on a 42 LCD tv?

High definition television uses one of three common formats - 720p, 1080i and 1080p. Any incoming signal will be delivered to a television in one of the three formats.

720p indicates that there are 720 lines in the image. The "p" means "progressive" and a complete image is delivered 50 or 60 times each second.

1080i shows that there are 1080 lines. The "i" stands for "interlaced" and the image is sent in two halves so a half image is sent 50 or 60 times each second but the full frame is sent only 25 or 30 times each second.

1080p is also made up with 1080 lines but the "p" shows that a full image is delivered 50 or 60 times each second.

Broadcasters use 720p or 1080i. These are both full HD signals. Although the 720 line image has a lower resolution, it is updated twice as fast. The data rate for 720p and 1080i is the same. Although 720p is less common than 1080i, it is used by broadcasters for some fast action content such as sports.

1080p updates the image at twice the rate of 1080 and therefore uses double the bandwidth. Broadcasters do not send out 1080p and it is restricted to local sources such as Bluray, games consoles etc.