You may heard some television sets being called HD TV and some Full HD TV.

In other words they are called 1080i and 1080p respectively

Although current models are mostly Full HD TV sets, you’ll need to understand the difference between the two especially if you’re thinking about buying an older used set.

Full HD TV is often referred to as a 1080p set and HD as 1080i.

1080p means 1080 lines in progressive mode.

1080i means 1080 lines in interlaced mode.

Scanning

When image is displayed on video this is the scanning which takes place in an 1080p TV.

The scanning takes place from A to B. It jumps from A to B straight. Therefore is called progressive.

…………A……….
…………B……….

In 1080i TV scanning takes place from A1 jumping over B1 to A2 before moving to B1 and then jumping to B2

…………A.1………
…………B.1………
…………A.2………
…………B.2………

In progressive video every single line is a sequence.

In interlaced video alternate lines (A1 + A2)  form a sequence.

Frames vs Fields

1080p is frame-based video. In other words, it is referred to in frames per second.

1080i is a field based and is expressed in fields (A1 is a field and A2 is a field) per second.

A field contains half the lines of a frame.

For example for a PAL system TV 1080p will have 25 frames per second. (A + B)

1080i will have 50 fields per second. (A1 + A2+B1+B2)

Quality Difference

What does this mean in terms of video quality?

Generally you’ll not see much difference between the both. Both have a resolution of 1920 x 1080 pixels¬† (2.1 Megapixels)

However, 1080i will show its shortcomings when it comes to full motion video, 1080i show jitters when subjects in the video move diagonally or vertically.

So, if you’re watching fast moving action you would have a better viewing experience over 1080p.