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Fw: 2 Q's: Digital dropouts & low con prints
- To: "telecine internet group" <telecine at alegria.com>
- Subject: Fw: 2 Q's: Digital dropouts & low con prints
- From: "Christopher Bacon" <KA2IQB at worldnet.att.net>
- Date: Mon, 24 May 1999 15:56:45 -0400
- Resent-Date: Tue, 25 May 1999 09:38:19 -0500
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John McDaniel writes:
>To what degree are you experiencing dropouts with digital tape formats like
>DigiBeta, etc? I looked at the transfer of a film project to DigiBeta and
>there were both video and irreparable audio dropouts (couldn't layback the
>audio after multiple attempts). [...]
This is not typically problem with Digibeta, which is actually quite robust.
However, there are several things that can cause this problem with any tape
format: a bad piece of stock, poor environmental conditions (temperature,
humidity, dust and dirt), and machine or edit controller problems. The
smaller the tape format is, the more likely it is to be bothered by such
problems, by the way.
>On a possibly related note: I've been watching a lot of the re-broadcasts
>of "Homocide" on Court TV and nearly every episode suffers from quick
>giant horizontal pixel crawl dropouts at several spots in the broadcast.
Professional digital VTRs scramble each frame of data prior to recording, so
dropouts big enough to break through the error correction and concealment
are seen as sparkles or "digis" in a pseudo-random pattern on the screen.
Horizontal crawling artifacts are more likely a transmission issue.
>I'm seeing more dropouts in general on TV since the digital kind appear
>more noticeable than those old analog hits.
But compared to the "old" analog days of only 20-25 years ago, these hits
are less ojectionable than the "Oops, We're Having Technical Difficulties"
slides that TV stations used to keep in reach for when the heads on a quad
machine clogged up, or the TK-28 (or insert the name of your favorite film
chain) took a fit.
>Could someone kindly give a semi-technical rundown of the "low con print"
>concept? I basically understand, but there must be some art to this process
>because some of the low con prints I've seen come back from a lab/transfer
>facility look surprisingly bad. These are films originally shot for
There are several ways of doing this, depending on the type of film. For
color print, it is necessary to use a low contrast stock. Black and white
requires special processing (the film is developed to a different gamma).
Reversal films may be "flashed" (exposed to a controlled amount of light on
a printing machine) either prior to or during developing. So there is room
for a lot of variability here. Low contrast prints were very common in the
days when TV stations routinely went to air from film chains, as the
contrast range was a much better match to video, but there isn't so much
call for them today. (Modern telecines are far more sensitive than film
chain cameras were, and can deal with far more range).
>Does making a low con film print and then
>transferring it to video create particularly different challenges in the
>transfer to tape than transferring directly to video for a MOW broadcast
>that will never see theatrical projection?
There are no special challenges in transferring a low-con print compared to
a normal one, but it has to be understood that once visual "information" (in
this case, contrast and perhaps detail in the lows and highs) has been
thrown away by one process, you can't readily get it back.
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