Re: Fields - do I understand correctly?

If you move or scale interlaced video in the comp you must separate fields. Moving interlaced footage up or down an odd number of pixels will reverse the field order and really screw things up if you don't separate fields.

Any time you use a camera and place interlaced video in a 3D layer that's not perfectly square with the camera and at the default distance you must separate fields.

About the only time you can not separate fields and be guaranteed that you're not loosing quality and risking all kinds of output problems is if you just drop the video into the new comp icon or into your empty comp window or timeline to create a new comp with exactly the same properties, and then you don't touch any of the transform options other than opacity. OTT, you should always separate fields.

If you want to see every field, you double the frame rate of the comp.

When you render you can choose to introduce fields or you can choose not to introduce fields. This is an artistic decision and has no other effect except for how the rendered product will look. Interlaced video for the web generally looks terrible. Interlaced video for TV generally has a smoother feel to motion. Non interlaced video for TV means that the set will still display fields but both will be the same moment in time so the results will have similar motion characteristics as film. They won't be exactly the same, but they will be similar because of the different way the shutter works in film cameras vs video camera.

There are even differences in the way motion looks between film cameras. Most motion picture cameras have rotary shutters that have the shaft to the right side of the frame and they rotate counter clockwise exposing the film from the bottom of the frame to the top, but others have the shaft below the frame exposing the film from left to right. These two types of shutters produce different motion artifacts just as a video camera, which scans the frame from top to bottom every other line, then goes back and picks up the missing lines twice per frame and 60 times per second (50 pal) in the standard way produces different motion artifacts than a video camera that's truly progressive and records the entire image for each frame. When shooting, especially panning, you have to take great care not to introduce a stroboscopic effect with both film cameras and progressive video cameras. When creating moving elements for non interlaced or progressive output you have to be very careful that you don't end up with the same problem. Whether or not to separate fields is a much easier question to answer than whether or not to render interlaced for TV. Move, scale or rotate, separate. Render with fields, depends the motion in the frame and on how you want it to look on TV.