Suggestion for CV Review

3 replies [Last post]
ps
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Joined: Feb 28 2001

Firstly: Appologies if this has already been done and I have just missed it.
Secondly: Appologies if this is/was somewhere within this board and again I have missed it. (I did search but couldn't find anything.

OK, get out safety clauses now issued, I should be safe to carry on.

Could CV mag do a review on tapes? DV, VHS, S-VHS, 8mm etc. I have chatted to several people, including people at duplication houses about the positives and negatives of different brands and models, but I have not found an answer. Personally I am very interested to get people's opinions on VHS tapes, as I find that most DV tapes are the pretty much the same quality (I know sweeping statement, but other than a sony deck that doesn't always like the timecode from a panasonic tape, I can't see that much difference). With VHS, however the difference between tapes can be huge when copying from either PC or DV.

Perhaps a review of the different VHS tapes on the market would be of interest as lets face it, however poor quality it is in comparison with many of the other formats out there, I guess it is probably the most widespread format for actually recording to once you have edited all your footage?

Even if a review is considered too boring, I would be very interested to hear the experiences of others here to try to find the best quality VHS tape I can use for preview tapes and for final copies.

As another question to be thrown in, would putting a kramer booster in between my DV camera and my video deck (Pana AG 4700) increase the quality of the picture? Although I am happy, I do find the picture looks slightly washed out, in comparison with the original DV signal. I know it is not going to be a good as the DV picture, but it is not quite a good as I would like.
I am also going to look into replacing my leads as I believe this will help matters, so any thoughts there would be gratefully received (though I know this has been discussed in other threads, so I will do another search)

For reference, I am inputing using the y/c socket and onto Fuji SHG tapes.

cheers

PS

Alan Roberts at work
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Joined: May 6 1999

I know this isn't the answer you want, but I dropped a piece in the FAQ forum recently on DV ADC/DAC performance. It explains some of wht you see when you make copies from DV. The best thing you can do, I suspect, is to apply a frequency compensation to the luma channel, giving about 2.5dB boost at 5MHz. That'sll keep it sharp looking, but you'll lose dramatically via VHS because there's little if anything above 2MHz on the VHS tape, and chroma bandwidth is about 300kHz if you're lucky.

But the differences between brands and quality levels are really much more to do with the noise performance of the tape, and the propensity to drop outs, than resolution. DV (and Digital8) wins because the recording's digital, you get a 100% accurate clone when you copy, provided there are digits to be recognised. The only problem comes when the tape wear/damage is enough to tip the copying device (DAC, other VT whatever) over the edge and it looses the signal completely. Preofessionl digital VTRs have signal condition metering so that you can check the error rate on tape, that gives a good indication of when it's going to go wrong. In DV we have to keep our fingers crossed and guess when disaster's creeping round the corner.

I like the idea of an in-depth article on all this though.

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alan@mugswellvillage.freeserve.co.uk. Delete village for a spam-free diet.

ps
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Joined: Feb 28 2001

Alan

Many thanks for your advice. With regard to boosting the luma channel, though, are you advising I use a y/c to BNC split cable to break the two signals apart and then only boost one of them? or is there a piece of kit out there for doing this. I seem to remember when I used to use Sony 1024's that they could boost specific channels, however I don't remember being able to be as specific as frequencies. Even if they could, I most definitely don't have the budget for one of them! I will re-read the previous thread you posted. I do remember looking at them, however I had had a particularly busy day and with the amount of technical stuff that was in there it was a little bit like a truck driving straight through my head and I didn't take a great deal of it in first time round.

cheers

Paul

Alan Roberts at work
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Joined: May 6 1999

OK Paul, I know how it feels.

Generally there's little you can do. With the S cable, if you split it into luma and chroma channels, there's a chance you can do some twiddling. Don't touch the chroma channel at all, leave it alone; since it contains the colour burst as well as the chroma, and the display decoder uses the amplitude of the burst to set its agc, tweaking this channle does nothing except introduce noise, which you definitely don't want to do. To might find some equalisers that do it right, but they'll cost a fair bit.

I'm not really adviusing you to do this, just explaining what happens if you do. If you use a decent processing amplifier, you'll find that it has functions like "luma hf boost", "chroma hf boost", luma/chroma timing adjust" and so on. You can do it the hard way (I usually do, just for masochism's sake) but the best way's to use decent kit designed for the purpose. Of, course, that begs the question "what's decent kit?" and that's where the article you requested comes in.....

My comments about DV DACs relate to the absence of Sinx/x equalisers in all of them (apart from the real pro stuff). That causes a gradual droop in hf performance, details in the FAQ. Equalisation for it applies a gentle lifting of the hf, peaking to about 2.5dB at 5MHz or so. Nothing dramatic, and probably not worth even thinking about if the output's going into VHS, even SVHS might not really benefit significantly.

Hope that's helped.