This is topic Reason of inferior sound reprodution of silver tracks with red light reader? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.


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Posted by Martin Heilmann (Member # 2607) on 04-11-2010, 11:48 AM:
 
Hello friends!

Now I would like to write my first posting here and first of all I would like to introduce myself:

My name is Martin, I come from Germany, I am 32 years old, I have studied mechanical engineering for diploma at the university of dortmund and I am intrested in cinema projection for ages and I am a cinema projectionist for ages.

Max and I were invited from Brad Miller last year to see the ShoWest in Las Vegas.

So, my question:

Would You be so kind and talk about the reasons of inferior sound reprodution of silver tracks play on red light readers? I am able to regognize fizzling "sss" sound and light distorted "aeiou" sounds.

Heard that is due to cross modulation problems?

In my home projection booth I started now with the red aera using the luxeon LED. My Processor is the CP200 with newest cards inside. Silver Track with white light sounds superiour, cyan tracks with LED, adjusted slit optic in focus and switching on the second projector input sounds surprisingly superior, too.

Last week Max was here and we played some first reels of some films. One first reel had some light acoustic noise on the "aeiou" sounds. It was the titel "vantage point".

At last we played a whole silver print, half film with red LED an second half with white lamp. Sound quality was noticeable better with the silver track.

So I would like to know the reason for inferiour sound quality when playing silver track on red readers.

Nice to hear from You,

yours sincerely

Martin
 

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Posted by Monte L Fullmer (Member # 2797) on 04-11-2010, 05:29 PM:
 
Welcome as always. My strong guess is the resulting color. As you noticed that the cyan track of current prints and the red light from the LED are on the opposite end of the color spectrum and when red light mixes in with the cyan track being blue, you have solid black as a results.

With the older silver tracks, the results won't be this black as mentioned, but a lighter color result and this is where your noise is coming from.

Others will probably chime in on this topic, but this is my probable guess.

-Monte
 

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Posted by Sam D. Chavez (Member # 1841) on 04-11-2010, 06:06 PM:
 
Monte,

Nice starting point.

The cross modulation is the main issue. To put it simply, all variable area soundtracks, indeed all developed film for that matter, is by definition, either slightly under or over exposed.

This effects the soundtracks because the peaks and the valleys are either etched away too much as in over exposed, or filled in as in under exposed.

Crossmods are the test of correct development and are taken on a densitometer with the specific light spectrum. For many years the standard was the IR spectrum of the tungsten exciter bulb. This was changed to a 660 Nanometer Red LED for any number of reasons that have been discussed here ad nauseum before.

So, the transition to Cyan occured and the crossmods are now optimized for Cyan tracks with the Red LED in mind.

When you play a silver track with a Red LED the results are less than optimum but mostly satisfactory to most people, but does vary according to the original quality of the development.

The best way to play silver tracks is with a tungsten light bulb, the best way to play Cyan tracks is with the appropriate RED LED and reader.

BACP readers are the only red readers with an interchangeable red and IR LEDs. There is still an issue even with my readers as the focus point is slightly different for a Red LED vs. an IR LED but it's the best way to optimize both.

OK, Steve G, bring it on.
 

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Posted by Phil Hill (Member # 371) on 04-11-2010, 06:30 PM:
 
I wish someone would make a modification kit for a 5-Star soundhead tungsten light bulb source with a red led source as well. You know, in place of the basement digital reader (there are penthouses for that), they would leave the original tungsten light bulb in place and the stereo cell and have the reverse analog red reader replacing the digital reader.

That way one could choose between the best sound reader for the film they are screening.
 

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Posted by Sam D. Chavez (Member # 1841) on 04-11-2010, 06:35 PM:
 
Phil,

That is the purpose of the IR LED. It sounds like a tungsten light bulb and offers the even illumination and better characteristics of the reverse scan reader and solar cell.
 

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Posted by Phil Hill (Member # 371) on 04-11-2010, 06:51 PM:
 
Sam,
I'm a little confused...

I have your reverse red analog reader in my home screening room... should I replace the red LED source with an IR version to get the best performance on silver as well as cyan tracks?

Any drawbacks?
 

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Posted by Sam D. Chavez (Member # 1841) on 04-11-2010, 08:41 PM:
 
Must have been that Bloody Mary with my lunch.

Red LED's and a reverse scan readers are the optimum way to play Cyan tracks and will play silver tracks well but not perfectly.

IR LED's and a reverse scan reader are the optimum way to play silver tracks and will play Cyan tracks very poorly.

Of the reader brands around, BACP is the only one with interchangeable LED modules so you can optimize.
 

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Posted by Monte L Fullmer (Member # 2797) on 04-12-2010, 02:25 AM:
 

quote:

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a modification kit for a 5-Star soundhead tungsten light bulb source with a red led source as wel

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