Image quality in old videotapes

[Electronic M]

I know I've gone as far as three maybe four generations of copying in the VHS format, and despite tons of garbage getting in each time they were still rather watchable (though using a video stabilizer during dubbing would have helped greatly).

I'd bet that with a good stabilizer during dubbing, tapes without bad sections (I often find one or more spots on a VHS tape that will play back with a noise streak even after the tape has been recorded over! ), some type of filter to prevent line noise from getting to the decks, a metal cage around the equip to prevent pickup of STRONG RF noise pickup, properly functioning VHS decks and a procedure of maticulously checking a copy for flaws (and rejecting flawed copies) before copying it again one could probably get a VHS tape to remain watchable out past 10 generations of copy (probably even farther for S-VHS-ET recorded VHS cassettes).

[Sandy G]

I don't think the VHS Overlords ever thought we'd be tryin' to save our Stuff..

[Rinehart]

Originally Posted by Electronic M

I know I've gone as far as three maybe four generations of copying in the VHS format, and despite tons of garbage getting in each time they were still rather watchable (though using a video stabilizer during dubbing would have helped greatly).

I remember seeing a show called The Secret Life of Machines, a British series that examined the history of everyday pieces of technology: washing machines, sewing machines, refrigerators, etc. I remember there was one episode magnetic recording, where they showed how audio tape may be made with Scotch tape and rust: take a piece of Scotch tape, rub it in a pile of rust powder, shake off the excess, then run it through a reel-to-reel tape recorder. The message they recorded was "this recording was made with Scotch tape and rust," which didn't sound bad at all when they played it back.
They also talked about video tape, and how the image quality of a video cassette--I don't recall if it was VHS or Beta--degraded very quickly as one tape was copied to another, which was then copied to a third. By that point it was just possible to see the image--a BBC 4 ident--but a fourth copy yielded no recognizable image at all. They explained why this was, but it will come as no surprise to anyone here that I didn't understand it...

[tvcollector]

I find the image quality on some old home movie Beta tapes I recorded back in the 90s, the quality of the image looks as good as the day they were recorded.... I find that tapes will last much longer than DVD's and CD-Rs... #1 the simple fact that the tape is completely protected by the cassette shell, unlike DVD and CD where even oils from your skin is harmful. I'm a Disc Jockey and I handle discs alot, and I see on these cheap CD-Rs where the oils has deteriorated the disc on the sides, and even some spots on discs where you can see seethrough holes in the material of the discs.. Believe it or not, the "Disk" technology is on it's way out.. I can see even those flash memory sticks are going to be a BIG way of storing audio and video, Even the new TVs these days are being made with USB ports.. I remember those days we disc jockeys used those, what the new generation calls "those BIG black round things", "Vinyl" which Disc Jockeys abandon, believe it or not, not too long ago back around 2005, 2006... And Vinyl even holds up much better than those CDs.. Now a laptop and a $400 DJ program which comes with gear is all we need, as disc jockeys are now starting to abandon CD...

[Phototone]

The problems with small analog video tape formats are these: The color signal is recorded very low resolution (heterodine color), the signal to noise ratio of the recording is barely acceptable for the original first generation recording, the time base of the recording is unstable, and barely acceptable on first recordings, and the errors are exaggerated on dubs (severe flagging at top of screen). Just try viewing a second or third generation VHS dub on a TV made before home video became possible. Later TV sets were designed to somewhat compensate for the time-base issues. Oh, and the average unit, VHS, Beta, U-Matic only resolves about 220-240 lines of resolution, which was barely good enough, considering the potential video could have 440 lines of resolution.

[old_tv_nut]

Originally Posted by Rinehart

...They also talked about video tape, and how the image quality of a video cassette--I don't recall if it was VHS or Beta--degraded very quickly as one tape was copied to another, which was then copied to a third. By that point it was just possible to see the image--a BBC 4 ident--but a fourth copy yielded no recognizable image at all. They explained why this was, but it will come as no surprise to anyone here that I didn't understand it...

Don't know what explanation they gave, but part of the problem was that home tape formats had very strong edge enhancement to attempt to make up for the lack of real frequency response, plus noise coring to eliminate tape noise, which also also would lose any low-contrast fine detail. Proper copying decks would turn off this enhancement stuff to try to get a copy as close to the first generation as possible. Otherwise, you'd increase the overdone edge effects on each generation.

Edit: Plus the multiple stages of noise coring and the ever decreasing chroma frequency response would smear everything into looking like a flat area with outlined edges, sort of a smeary "paint by numbers." Also, home formats used comb filters to separate the adjacent track signals and the "color-under" signal from the luminance, so there was increasing vertical smear of the color also as you went from one generation to the next.