Sunday, December 02, 2007

Any video buffs out there?

I have a question and I don't know where to find the answer. What I need here is someone who knows all there is to know about videotape technology.

Here's the question. When you reuse a tape, is the previous recording always erased completely? Are there any circumstances, ever, where a previous image might show as a faint overlay on the new recording? Or is it an absolute that the previous recording is definitely gone for ever, and no trace of it could remain?

It's an important matter to me, because it would mean that every investigation would need a fresh tape. No re-use. Expensive, but if it's necessary, I'll do it. Or maybe I could dump all the tape-driven cameras and use hard-disk ones instead. They can't have this problem. Or can they? What about those solid-state ones that use memory cards? Surely reformatting the disk or the card would clean everything off it?

Anyone know?


tom sheepandgoats said...

I'm not an expert, Romulus, but I would buy a fresh tape each time. Or is there some devise that is only for erasing? But I would never just tape over something and trust the original leaves no trace.

On a sound cassette tape, one can sometimes hear echoes. Others know the cause better than I, but it is enough for me to know the process is flawed and not to trust it for anything I consider critical.

tom sheepandgoats said...

HA! Reading your back posts I see you've been having at it with Dikkii. I suggested he check out your field of research and boy, has he ever. Alas, it's too long for me to read at the moment, but I will very soon.

Dikkii's a good fellow, from my experience with him. He writes and thinks clearly. He does not give up.

Dikkii said...

Nice of you to say, Tom. Thank you.

Romulus, I'm reliably informed that digital doesn't have this problem. 'Course you can re-format to be on the safe side.

Romulus Crowe said...

Hard disk it is then. I'll replace those videotape cameras as time and budget allows.

It was the Valentown footage that set me thinking this way. I watched it again, and recalled the old TV's of my youth. You had to tune them manually. Nowadays you just press a button that says 'find all the channels'.

In the UK, we have BBC, and a collection of regional independent stations. If you lived near the border between those regions, sometimes you could get both independent channels. Usually you'd get one, and the other was fuzzy and faint.

Tuning could be a trial because sometimes you'd pick up the faint channel as an overlay on the stronger one. It just made the image fuzzy unless someone moved within that faint image. Then you'd see a 'ghost' wandering across the screen. Fiddling with the tuning knobs usually fixed it. Eventually.

So I wondered if something similar could happen with videotape. An older recording, not quite erased, showing as a ghostly image on the new recording.

If it's at all possible, then it would be silly to take the risk.

Romulus Crowe said...

Oh, and Tom - that casual comment on cassettes just threw doubt on all those EVP's recorded on tape, you realise? ;) Certainly on any that were recorded on re-used tapes.

I have a digital voice recorder already, because no moving parts means far less interference. I also reformat each time because it's easier than deleting the files. Phew!

Dikkii said...

I have a digital voice recorder already, because no moving parts means far less interference. I also reformat each time because it's easier than deleting the files. Phew!

There's been advances in solid state memory which means a lot fewer moving parts - which is good - less power usage.

Unfortunately, backlit colour screens wipe out a lot of these gains.

Romulus Crowe said...

I've never understood why a voice recorder would need a colour screen. Mine is monochrome. It does have a backlight, and that does use power but it's set to be on for the minimum time required to be sure it's recording.

Another thing I made sure of when choosing it was that it takes standard batteries, alkaline or rechargeable, so I can carry spares. Those with a fixed internal rechargeable battery can die in the field and there's nothing you can do about it.

They're also junk as soon as their battery stops accepting charge.

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