HDTV Glossary: Interlaced or Progressive Scan - What is it?

One of the more popular questions asked by people looking to dip their toes into the HDTV market place is just What is the difference between a Progressive Scan and Interlaced picture. Well simply put, Progressive scan screens draw all the lines on the screen at once, however on an interlaced screen the picture is rendered in two (albeit incredibly fast) stages. The first stage draws every other line on the screen, (think of them as the odd numbered lines). A split second later the even numbered lines are filled in. This happens so quickly that the naked eye is fooled into thinking it is seeing one image. So 720p or 1080p screens draw 720 or 1080 lines of the image in one go, whereas a 1080i screen contains 1080 lines of detail rendered in two stages. The 1080i image will contain more detail than the 720p but there will be some flickering and jagged edges when watching fast moving scenes. The popular consensus is the interlaced image is fine if you want to watch movies, but if you are interested in sport then its better on a progressive scan screen.