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Re: Noisey Transfer impossible Question.
- To: telecine at alegria.com
- Subject: Re: Noisey Transfer impossible Question.
- From: <KA2IQB at aol.com>
- Date: Fri, 3 Jul 1998 12:48:20 EDT
- Resent-Date: Fri, 3 Jul 1998 09:50:49 -0700
- Resent-From: telecine at alegria.com
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The kind of artifact you describe sounds like digital hits, or "digis," which
could come from just about anywhere in the production chain. To go further,
it would be interesting to know what size they are. If they are blocks
several pixels wide or high, it could possibly be DCT error in the DigiBeta;
one pixel wide/high is usually a bad cable or a malfunctioning piece of
I'm kind of surprised to hear that you couldn't compare the material with and
without noise reduction in the telecine session. It's only the press of a
button in most installations to switch the noise reducer in and out to see the
difference it makes, so that shouldn't have been an issue unless they were
already laying the material down to tape.
Mainly due to concern about noise reducers and color correctors that make film
look so good that DPs and producers can't see the defects until they go to cut
the negative, some facilities are offering direct-to-tape transfers that
bypass much of the usual processing in a telecine suite. These have their
place as "video checkprints," but one would not ordinarily want to edit or use
them for post work. There are two technical reasons why. First, noise causes
all kinds of problems if the video is going to be compressed, as is often the
case nowadays. Assuming the compression scheme can even deal with the noise
without breaking down, it will produce a much higher bit rate (i.e. it will
not work as efficiently) as it would with a clean signal.
The second reason is the general nature of video. You've probably heard the
term "signal-to-noise ratio" before. Basically, it means the ratio of the
desired information (image) to the noise, which is everything else in the
picture. It behooves us to make this ratio as large as possible at the
beginning because practical electronic circuits only handle finite amounts of
power over their given bandwidths. The more of this "space" you waste on
crud, the less remains for useful signal. With modern video equipment, the
film and/or telecine are the noisiest parts of the whole chain, so doing noise
reduction in telecine suites is actually the best place for it.
Thanks to Trans/EFX Systems for supporting the TIG in 1998.
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