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Author Topic: random question
Alan Plester
Expert Film Handler

Posts: 209
From: great yarmouth england
Registered: Apr 2001


 - posted 08-06-2016 03:56 PM      Profile for Alan Plester   Email Alan Plester   Send New Private Message       Edit/Delete Post 
Hello everyone in cinema land, can you experts answer a question for my daughter who wants to know...
On old films if it was credits on a black background what made the cracklings of white?
I just know one of you will have the answer,
thanks in anticipation

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Harold Hallikainen
Jedi Master Film Handler

Posts: 906
From: Denver, CO, USA
Registered: Aug 2009


 - posted 08-06-2016 04:21 PM      Profile for Harold Hallikainen   Author's Homepage   Email Harold Hallikainen   Send New Private Message       Edit/Delete Post 
Is the "crackling of the white" referring to watching an old movie on TV? If so, that should not happen any more unless the video is converted to NTSC RF and sent to the TV. NTSC uses (used?) a vestigial sideband AM signal to carry the video and an FM carrier 4.5MHz above the video carrier to carry the sound. Very early TVs used two receivers, one for the video, and another for the sound. In 1948, Louise Parker patented the "intercarrier method" for television. It was realized that there is no difference (especially for vestigial sideband where the lower sideband only goes to 1.25MHz or so) between two carriers separated by 4.5MHz and one carrier with a subcarrier of 4.5MHz. In an intercarrier transmitter, the sound carrier is generated at 4.5MHz and added to the video signal, which then drives the AM transmitter. On the demodulator side (in the receiver), the demodulated signal consists of the analog video with a 4.5MHz signal above the video. That 4.5MHz is frequency modulated with the sound.

However, when you amplitude modulate a carrier, you have to be careful to not go over 100% modulation ("carrier pinchoff"). Since NTSC video uses full carrier for sync, near full carrier for black, and low carrier for white, when you combine the FM subcarrier with the video, white MAY cause overmodulation. If the video carrier entirely disappears due to the white (typically text), the FM subcarrier also disappears causing the sound to come and go as the various pixels are transmitted.

So, IF you were talking about white credits on old movies as seen on an NTSC TV, that's probably what happened. If that's not what you're talking about, it isn't!

After the fact, noticing that you are in England, you did not have NTSC television, but intercarrier was used in all analog television systems throughout the world.

Speaking of British television, 25 or 30 years ago, I saw a television program about the first 50 years of television at the BBC. It was great! They covered the Baird system, various mechanical systems, etc.

Thanks!

Harold
(who used to work in broadcasting)

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Alan Plester
Expert Film Handler

Posts: 209
From: great yarmouth england
Registered: Apr 2001


 - posted 08-06-2016 04:28 PM      Profile for Alan Plester   Email Alan Plester   Send New Private Message       Edit/Delete Post 
Wow! fast answer, many thanks for that Harrold, appreciate it.

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99


 - posted 08-06-2016 04:59 PM      Profile for Brad Miller   Author's Homepage   Email Brad Miller       Edit/Delete Post 
Teaser subject titles are not permitted.

Tick...tick...tick...

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Steve Kraus
Film God

Posts: 4094
From: Chicago, IL, USA
Registered: May 2000


 - posted 08-06-2016 06:16 PM      Profile for Steve Kraus     Send New Private Message       Edit/Delete Post 
Alan, you need to edit the title of this thread to reflect what it is about.

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Leo Enticknap
Film God

Posts: 7474
From: Loma Linda, CA
Registered: Jul 2000


 - posted 08-06-2016 07:46 PM      Profile for Leo Enticknap   Author's Homepage   Email Leo Enticknap   Send New Private Message       Edit/Delete Post 
If you're watching a film projection, then white artifacts (specs, lines, etc.) could be dust and scratches that were present on the internegative used to strike the print, and were printed through - black on the neg, white on the print. That wouldn't just be in white-on-black titles, but negative scratches and dirt would certainly be very noticeable there.

Since the 1980s, internegatives were ultrasonically cleaned after a given number of passes through a printer, and so negative dirt and scratching on a typical release print from the '80s onwards was almost zero. But lab cleanliness wasn't as efficient going back further, and so you do tend to see more negative crud on original release prints of older movies.

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Carsten Kurz
Film God

Posts: 4340
From: Cologne, NRW, Germany
Registered: Aug 2009


 - posted 08-07-2016 01:19 PM      Profile for Carsten Kurz   Email Carsten Kurz   Send New Private Message       Edit/Delete Post 
Alan - can you be more specific as to what you or your daughter mean with 'cracklings of white'? When/where do you experience them?

- Carsten

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