Interlace and Progressive Scan for video

i for interlace - p for progressive

many people confused with what is interlaced and what is progressive scan in video term.

Interlace in Wiki

Progressive Scan in Wiki

Interlacing is a clever technical trick used to minimize picture flicker on your TV. With interlaced scanning, a TV frame is composed of two fields. One field is made up of all the odd numbered lines, while the other field is made up of all the even numbered lines. These interlaced fields are usually refered to as 50i for PAL shooting (60i in NTSC) and the frame rate is very similar to how the eye sees the world (giving a natural-looking motion blur). If you have an old fashioned (CRT) TV - and watch the news and docs then you are watching interlaced pictures.

Progressive scanning scans the whole picture frame from top to bottom (like reading a book). If you watch programmes on a Plasma screen, LCD or DLP (Digital Light Projector), then you've already been watching pictures displayed in a progressive mode (although not necessarily recorded progressively).

With cameras, progressive scanning usually leaves us with 25 frames, often refered to as 25p (30p in NTSC). This gets some people very excited, because film is also shot at 24 (or 25) frames per second. A camera that shoots true 24/25p will give you a film look without all the costs associated with film production.

If you are on a low budget and want to make video look like film make sure the camera shoots true 24p or 25p. The JVC HD100 and HD101 does. The Sony Z1 and Canon XLH1 do not. The Sony has a cineframe option and Canon just calls it Frame and refer to it in its specs as 25f (to distinguish it from true progressive - 25p). See Adam Wilt's site for his explanation on what Sony's cineframe is all about. The jury is still out on how Panasonic will process 24/25p.

For a very good explanation with animated pictures on progressive and interlaced pictures see www.avdeals.ca/classroom/Proscanexplained.htm - it is more biased to the American audience but the explanation should still be of use to us PAL people. There is also a good explanation of interlaced and progressive scan at Avis communications.

I'd also recommend you look at the excellent Ken Stone site for more info on 24/25p and editing (with Final Cut Pro)