If the tape is just standing still, shouldn’t the image be clear? What are those lines caused by when pausing, fast-forwarding, and rewinding a video tape?
When a tape is recorded, the helical heads lay down tracks that are angled with respect to the tape. Sort of like this /////// only at a much sharper angle. When the tape is stopped or running at a different speed than it was recorded at, the heads don’t align correctly with the recorded tracks. Four-head VCRs have a second set of heads mounted at a different angle to compensate, but it’s still not quite perfect, so there are some artifacts introduced. This is a bit of a simplification, but I hope you get the general idea.
Interesting…thanks!
QED
I’ve heard that the reason the tracks are diagonal is so that the tape won’t be so wide. Is that correct?
Actually it’s so that the heads can have a high rate of speed relative to the tape and still keep the cassettes a reasonable size. Because of the large bandwidth of a video, the tape must move past the heads more quickly than for audio. You can do this by running the tape past a static head very fast, or by moving the tape at a slower speed while spinning the heads. The diagonal tracks allow the heads to spin and not overlap the tracks.
Another important reason is that video frames do not exist independently like film frames. They are composed of two interlaced electronic fields. With consumer electronics, you technically are never pausing on a single “frame” like you would if you stopped a reel of film.
It really depends on the quality of the machine. 4 heads are generally better than 2, a well maintained like-new machine is better than one that has had rental tapes run thru it. A newly recorded tape (on that machine) is better than a well used tape. Etc.
Cheaper VCRs just read the same pair of frames over and over. Better ones use a frame buffer, read once (while the tape is still moving) and then redisplay from the buffer again and again. A much better system, more $ of course, but still can have artifacts.
The best freeze frame on any VCR I have owned is a quite old 2 head Toshiba Beta. Absolutely perfect. Go figure.
Also note that each frame of a video is not crystal clear. There is a certain amount of blur put into each frame to make it flow as opposed to jerking along at the fairly low frame rate TV has.
I got a Panasonic 6-head VCR from a commercial duplicator who was upgrading for $50…by far the best-quality images, still or in motion, of any I’ve ever had…
That’s complete bullshit. The frame rate of movies you see in the theater is even lower (24 fps) compared to TV (30 fps, interlaced at 60 fps). Blurring is an artifact of rapid movement, not any sort of deliberate attempt to smooth out the motion.