Interlaced video refers to video that is divided into two fields (upper and lower). Video standards that use interlacing are NTSC, PAL, and SECAM. In interlaced video, an image is drawn on the screen in two separate passes ? in the first pass, the first field of information is drawn; the second pass fills in the remaining information for the second field. Non-interlaced video (also called progressive scan) displays video by drawing it on the screen in a single pass from top to bottom.

The United States standard is 30 frames per second video. The field rate will be double the frames per second, since two passes are made to draw each frame on the screen (30 frames per second = 60 fields per second). So, using this standard, interlaced video draws 60 fields of information on a video screen every second. PAL and SECAM standards both draw images at 25 frames per second (50 fields per second).

If you?re working strictly with digital video (for computer displays), then you won?t have to worry about field settings. Computers display video on a monitor as a sequence of complete frames (non-interlaced). So, video formats designed for computers don?t use fields.

It is possible to play interlaced NTSC video on both Windows and Mac computer systems. Likewise, you can play a progressive scan video clip on an interlaced (NTSC) video monitor, since interlacing is a characteristic of displaying and capturing video, not an issue related to file formats. Ideally, it is best to diagnose interlaced field-related issues on an interlaced video monitor, since doing so on a progressive scan monitor is unreliable.
------------------------------------------------------------------------------------------------------------

The aim of an argument or discussion should not be victory, but progress. -Joseph Joubert, essayist (1754-1824)

Thank you so much for the reply.
NTSC = 30 FPS
PAL = 25 FPS

But isn't the stuff played in cimemas 24FPS? So when one shoots a film intending to show it in a theater, do they shoot it in interlaced mode? Then it is later deinterlaced and then resampled at 24FPS? If so, is it better to shoot 60 fields a second or 50?

Future Director,
Tyler Ives

I'm not entirely sure of the process of getting video onto film, but I am under the impression that each two feilds of video are printed onto a single frame of film. The difference between 25 fps (I work with PAL in NZ) and 24fps is so marginal that most of the time nothing is done about it.
That said I don't know much about NTSC but I assume that some sort of reasembly process is nesisary.

Make Love Not War!

Thanks guys! Oh, so if you are intending to show your movie on the big screen, is it better to shoot at 50 samples a second(PAL) or at 60 samples a second(NTSC)?

Future Director,
Tyler Ives

As a general rule (I'm biased) never use NTSC when you have the option of something else. Its a flawed system and to complicate things more its not a clean 30 its 29.somethingorother.

Make Love Not War!