HOW is slow motion done on a video recorder? A VCR or a hard drive works the same way as a motion picture camera, yes? That is, it records a series of stills so fast that they have an illusion of movement. Okay, but then HOW do they do slow motion by just running the tape, or the drive, slower? In old slow motion film you had to actually photograph the thing at a very high speed to later give the illusion of motion being slowed down. If a VCR or drive just records a series of stills at a set speed then how does running it slower make the actual motion seem to go slower? Seems to me it would just spoil the illusion entirely and look like a series of still pictures in a sequence with no sense of motion at all.
Video does not work the same way. Film captures on average 32 full frames per second. Video uses interlacing, you can think of it as 60 half frames per second. This makes it easier to slow, and show a fairly clear image. However HSF (high-speed film) gives truly clear slow motion.
Slo-mo is done by capturing at a higher rate than the playback. In movies its done by overcranking the camera to more than the standard 24fps playback rate. With electronic media it's a bit more complicated, but the same general principles apply. Usually this requires a special camera that can work at higher frame rates. No, those are three very different things. Motion picture cameras capture light onto photographic film. A VCR records electrical signals onto magnetic tape in a cassette. And a hard drive stores digital data. Completely different devices for completely different purposes. That's what cinema film does. Video doesn't capture stills, rather it uses a "flying spot" that is constantly changing position. The illusion of motion is similar, but the technique is very different. Running an analog VTR slower causes the read heads to pass over the same information multiple times. All that does is to stop the motion until the tape advances to a new field or frame. Technically that's stop motion, not slow motion. True slo-mo requires a higher recording frame rate than the playback frame rate. Yes, that is why running a VTR at a slower tape speed is inferior to actual slow motion.
VCRs have something that high-tech cameras lack: natural motion blur. If you've ever freeze-framed a tape, you've noticed, there's a decent chance the still has fallen on one of the blurry slides. These blurry transitions help create the visual illusion of movement and your brain will fill in the missing pieces. You really only need a few frames per second to enjoy a moving picture, and if there are blurry slides in the middle than the movement appears to be smooth, at the slight cost of lack of details, but that just makes it easier on your brain to make up middle values for the imagined animation.
