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Topic: LED versus Exciter bulbs

Stephen Winner
Film Handler

Posts: 57
From: Richmond,VA
Registered: Jun 99

posted 11-19-1999 08:33 PM

On our simplex XL's we have a small mirror that diverts some of the light from the Peerless Magnarc's into the sound head.

How would it affect operation to install a red gel somewhere in the light's path so that we can play the cyan tracks without converting? Converting this setup would be a nightmare! This can be done easily from the looks of the soundhead, and save plenty of trouble of trying to convert these things to LED

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Jim Alexander
Film Handler

Posts: 71
From: Greenwood, Nova Scotia, Canada
Registered: Nov 1999

posted 11-19-1999 10:36 PM

Being a relatively new theatre owner (who had no benefit of background information or manuals to go by) I've been forced to learn as I go. Many times I've gotten "blind-sided" by left field problems. The latest is the change over from Exciter to LED (living in the "sticks" sometimes means not getting up to date information. What is the story here and am I up the creek on this one.

We run Century-C projectors with Exciter Lamb mono sound pick-ups. Am I going to have to convert? When and where did this all come about?

Someone plase help?@#@??!??

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Lance C. McFetridge
Expert Film Handler

Posts: 135
From: Penn Yan, New York
Registered: Jul 99

posted 11-20-1999 08:05 AM

I have been reading about the switch to cyan sound tracks and the lack of theatres with the reverse scan capabilities with some interest. If in fact the industry is dragging it's feet to conversion, and by all estimates it is somewhere around $1k per projector, how will the industry ever switch to digital projection? Because I know if it digital is mandated, the toes of my shoes will be worn out.

lance

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 11-20-1999 03:13 PM

What make of soundhead diverts the magnarc light to read the sound?

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Greg Mueller
Phenomenal Film Handler

Posts: 1687
From: Port Gamble, WA
Registered: Jun 99

posted 11-20-1999 08:10 PM

One of the problems with just replacing the incandescent bulb with an LED is that the exciter light (incandescent) system relies a great deal upon infrared, which the incandescent has plenty of. The led has no infrared so the detector and the led are working at different frequencies (kind of). Because of this "mismatch" you get less gain and more hum (noise). The reverse scan units are tuned to read at the same "wavelength" as the LEDs so it works with a minimum of "noise" and "hum" . Also, I think if you compare prices, CE will beat out Kelmar.

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Greg Mueller
Phenomenal Film Handler

Posts: 1687
From: Port Gamble, WA
Registered: Jun 99

posted 11-20-1999 08:20 PM

Oh yah, The analog sound track up untill this point in time was coated with silver (something or other) which blocked the passage of the infrared and so the system worked. The shadow cast on the pickup was infrared free, because of the silver goop. But, when they convert to the new sound tracks the silver goop will go away and if you shine infrared on it it will pass right on through producing no shadow and the incandescent system will not work at all. The LEDs don't have this infrared problem so they will work.

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Scott Ribbens
Expert Film Handler

Posts: 118
From: Los Angeles
Registered: Oct 1999

posted 11-20-1999 10:39 PM

Which brings us to those theatres that have the infra-red LEDs. You can replace these with visible red LEDs. The companies are now making these replacement LEDs.

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Scott

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Bill Purdy
Expert Film Handler

Posts: 139
From: Seattle, WA
Registered: Oct 1999

posted 11-22-1999 11:57 AM

If the Infra Red readers you have are Component Engineering's, please look on our website <www.componentengineering.com> for information. A listing of available versions can be found under "Price Lists" and there are a couple of instructional things under "Technical Bulletins". Unfortunately it is a little more complicated than we all might wish because the 660 nm LED's have turned out to be different than what we originally expected. We had to do a much better job of heat management and we felt the need to make a safer power supply. You can use the old power supplies with the new LED's but there are a couple of easy mods that are needed for the protection of the LED's. If you are converting a full Analog/Digital version it is not quite so easy, but kits are available.

If you have more questions, please call.

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Bill Purdy
Comonent Engineering

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 11-23-1999 09:05 AM

Kodak's web site has a complete description of the industry plan to convert to silverless (cyan dye) analog soundtracks:
http://www.kodak.com/US/en/motion/support/sound/index.shtml

Dolby's web site also has information:
http://www.dolby.com

Many labs and distributors have already converted to the "high-magenta" (magenta dye + silver) soundtracks, which are compatible with BOTH red LED and white light (tungsten light bulb) soundheads. The "high magenta" tracks are more compatible with both readers than the old magenta+cyan+silver tracks. The first major release with "high magenta" tracks was "You've Got Mail".

The proposed cyan dye tracks are NOT compatible with white light readers, and would have very poor signal-to-noise on these old readers. Conversion to cyan dye tracks will not occur until the vast majority of theatres are using red LED readers, probably in 2001 at the earliest. Almost all new sound readers use red LEDs for the many advantages they offer, but older soundheads need to be retrofitted.

Digital sound is NOT affected by this change. None of the three digital sound systems require silver to be left in the film.

The industry conversion to cyan dye tracks is motivated by environmental responsibility --- eliminating the silver redevelopment step in the print processing gets rid of a very caustic chemical and one of the major sources of waste in lab operations. With cyan dye tracks, almost all the silver in the film will be totally recovered by the labs, helping the environment when old prints are scrapped or recycled.

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John Pytlak, Senior Technical Specialist
Worldwide Technical Services, Professional Motion Imaging
Research Labs, Building 69, Room 7419
Eastman Kodak Company
Rochester, NY 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243

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