8mm Forum: Red light for optical sound.

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Posted by David Park (Member # 123) on March 08, 2008, 02:58 AM:

Went to a talk on cinema sound last night. Learnt the 35mm prints now coming into use have a difference to the optical sound tracks. The chemicals used in the past to create the optical track are very dangerous so a new method is being used. This means instead of the present white light being used a red light has to used. Cinemas in UK are presently having thier projectors modified if not allready done.
There is also an improvement to sound quaulity. Yes digital is the usual form of sound today but if a fault occurs they default to the optical track.

Posted by Michael O'Regan (Member # 938) on March 08, 2008, 07:58 AM:

Thats interesting, David.
May I ask, who gave this talk on cinema sound? Was it an industry thing?
-Mike

Posted by Maurice Leakey (Member # 916) on March 08, 2008, 08:53 AM:

Solid state red LED exciter lamps are now replacing the old white exciter lamps. They work with the standard silvered sound tracks, the new magenta sound tracks and also the future cyan sound tracks.

Eventually silver will be removed from all film sound tracks to be replaced with cyan sound tracks.

The old white exciter lamps will read the magenta sound tracks, but will not read the cyan sound tracks which will need red exciter lamps.

For the present, all the existing silver tracks can be read with the red exciter lamps as well as the newly introduced magenta tracks.

Maurice

Posted by David Park (Member # 123) on March 08, 2008, 09:24 AM:

It was at the Widescreen weekend, this w/e, at the Bradford Film Festival. National Media Museums Pictureville cinema.
Dion Hanson who is an engineer and cinema techology historian, he used to be with Dolby Laboratories and was chairman of the Projected Picture Trust.

Posted by Osi Osgood (Member # 424) on March 08, 2008, 11:57 AM:

It may sound funny, but I really never understood the concept of the "exiter lamps".

Are they different from a standard small lamp and if so, why?

I love what they do, (optical sound) but i never really understood what makes an exiter lamp work.

Posted by Kevin Faulkner (Member # 6) on March 08, 2008, 12:33 PM:

So could we do away with the std lamp on our Elmo's and replace them with a more reliable Red LED I wonder.

I take it they use the high power LEDs which are now available?

Kev.

Posted by Jean-Marc Toussaint (Member # 270) on March 08, 2008, 01:19 PM:

Red exciter lamps come in different forms. Some use LED technology, other use a small type of laser (I have one of these on my 35 machine). Indeed the new cyan tracks sound better but you need arena-style amplification to back it up.
Some LED style fixtures are fitted with a standard lamp socket so it's dead easy to make the change. I've heard some people have used red filters in front of the old lamps with ok results.
I doubt that new 16mm prints will be made with cyan tracks so I don't see the use of changing the light on our beloved Elmo CLs. As the wiseman says "if it ain't broke, why fix it?".

Posted by Robert Wales (Member # 502) on March 08, 2008, 02:55 PM:

Cyan tracks have been standard in North America for at least three years now

Posted by Hugh McCullough (Member # 696) on March 08, 2008, 06:12 PM:

Here is a pic of all the sound tracks found on modern 35mm cinema release films.

Blue lines each side of the film: SDDS (Sony Dynamic Digital Sound)
Grey track between sprocket holes: Dolby SRD (Spectral recording digital). If you look closely at this track you can see the Dolby Logo in the centre.
Cyan track Optical sound. Can be played back in Mono, Dolby A, or Dolby SR.
Dotted white line: Timing track for DTS digital. (Digital Theatre Systems)
This sound is recorded on special CD type discs, and the timing track keeps the sound on disc in sync with the picture.
These discs need a special player. They can not be played back in an ordinary CD player.

At the moment there is no intention to release 16mm films with cyan tracks. Apparently there is not enough room on the projectors to fit the readers.

For more information about cyan tracks see these web sites:-
www.kodak.com/US/en/motion/support/cyan/faq.jhtml?id=0.1.4.15.8.4.10&lc=en
www.dyetracks.org/

Posted by David Kilderry (Member # 549) on March 09, 2008, 12:03 AM:

They have been in use for several years here in Australia too now. Some high magenta tracks (the transition track) still coming through, but by far the majority are cyan.

I actually cannot remember the last silver (black) track to come through our projection room.

For decades the optical sound track application has required a separate run during printing as there is no silver required in a modern Eastman style colour picture image, it is a throw-back to the B & W days. The soundtrack applicator was required to work at high speed with almost no margin for error and often created problems.

The silver used is expensive and the residue difficult and dangerous to dispose of. The cyan track is as simple as the picture image to print. With a regular white exciter lamp some noise may be evident on a cyan track print, hence the change to red LED's.

Most commercial cinemas have changed in the western world with home cinemas and remote cinemas in the sticks now the hold-outs. Our Century was converted using a Component Engineering system. Our Philips Todd-AO DP70's with Bay Area Cinema Products.

The entire issue caused a great battle for years; the cinema owner again being forced to make changes for no real benfit to him. It was a minor battle compared to the digital change occuring now.......and many years into the future!

David

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