What about digital? We have one visible light Dolby Digital reader that was already in place before we retrofitted the complex to all digital sound. All the others are LED.

Do I need to replace this reader with a new one?

Russ

 

On the one hand the visable light basement readers are a pain in that they tend to make the soundhead cramped and hot, they are more forgiving and cheaper to run. You could buy a box of 10 EPT lamps for the cost of one visable red LED...anybody can change the EPT lamp whereas the LED really needs to be aligned by a technician. The EPT lamp tends to work until it needs to be replace...the LED needs to have it's current increased throughout it's life.

Steve

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"Old projectionists never die, they just changeover!"
 

"The three prominent digital sound systems can and do accommodate dye only images for their digital sound or control data."

For a pdf copy of this report goto:
http://www.kodak.com/country/US/en/motion/support/dyetrack.shtml
 

The reason for switching the analog readers was because I was told that the new print process would not be read accurately with visible light.

Will the SRD printed info be equally un-readable as is the analog track? A slide projector bulb is visible light (and they said I'd never use my high school projection again!).

I am confused because we are still sending visible (xenon) light through the image and it is still hitting the screen.

I don't understand exactly why the exciters won't work, but I accept it. I assume that the same dyes would be provided across the entite width of the print. Can this affect the resolution on the digital reader as well?

If so, I will have my biggest auditorium playing in SR (through that nasty 222-SRA *g*) until I can get a new reader shipped!

I have asked this question almost everywhere, and I always get "HMMMMM" as an answer.

I have read the other posts here and I have not had any problems with SRD.

Just a curious question...

Russ

 

Could someone please explain why visible light will have problems with silver-less dye? (on analog tracks)

It seems that with the "more light/less light" system, (variable area) that it would work.

I am simply not a genious like the rest of you! I was taught to look at a scope and re-act!! (If in doubt of my results, to call Lonny!)

This poor man deserves some peace!

Granted, he always knows just what to say, but I'm a bit self concious.

It's kinda like pulling over and asking for directions while your girlfriend is watching!

*grin*

Russ

The Silver added to the analog soundtrack area greatly increases the contrast ratio between the black and clear. This is an optimum condition for the light spectrum output of lets say, a regular old exciter bulb. When the soundtracks are switched to cyan (greenish/blue...dark blue), that high contrast ratio will no longer exist if using an exicter bulb. In order to obtain a high contrast ratio to the cell with this cyan color, a red LED light source is required. The important difference here is the wavelength of light from the light source required for today's soundtracks vs the wavelength of light necessary for cyan soundtracks. Hope this helps somewhat...

 

Go into the darkroom with the red safelight on. (Better darkrooms have "orange-ish sodium vapor lights, I believe.)

Look at something that's blue under the safelight. It'll look black. Same idea with the soundtrack! By making the "exciter" red and the soundtrack blue/purple the "solar cell" will see black.
 

Early analog soundheads used gas or vacuum phototubes, which usually had a "S-1" spectral response that peaked at a wavelength of 800 nanometres (infrared). Tungsten bulbs were used as the exciter lamp. Tungsten bulbs produce both visible and infrared light.

Almost all early soundfilms were black-and-white (silver image). Silver efficiently modulates both visible and infrared light (it has "density" to a broad spectrum of energy). So B&W prints worked fine with the tungsten exciter lamps and S-1 response phototubes.

Dyes are relatively "transparent" to infrared energy, so silver was needed to modulate the light in old soundheads. Technicolor dye transfer prints used a special Kodak B&W print film as the "receiver" for its color dyes, so the Technicolor soundtrack was actually a B&W silver image.

When Eastman Color Print film was introduced in 1950, almost all soundheads still used tungsten exciter lamps and S-1 response phototubes. So special steps in the process sequence were developed, requiring TWO fixing baths, and a special viscous soundtrack redeveloper applied to only the soundtrack area to "redevelop" the silver after the process bleach step. The final print soundtrack contained cyan dye, magenta dye and silver, and worked well with tungsten exciter lamps and S-1 phototubes. But the special process steps required to get silver in the soundtrack added to the processing complexity and cost, and were a significant source of laboratory waste and water usage.

The advent of solid state "solar cells" did not significantly change the situation. The silicon cells usually had significant response in the infrared, and lower efficiency in the visible portion of the spectrum. When used with a tungsten exciter lamp, most of the sensitivity was still in the infrared, so silver was still needed. Trying to create a visible-only response with a red filter or cell sensitive to only visible light was not practical, as the efficiencies were poor, and signal levels were much lower.

The invention of high brightness visible red LED light sources for sound readers finally allows the use of cyan dye-only soundtracks, since they have little infrared energy and do not require silver in the soundtrack for efficient modulation. Solid-state red LED readers have significant advantages for theatres, and all new soundheads use red LEDs rather than tungsten exciter lamps.

Eliminating silver from the soundtrack will significantly reduce processing cost and waste, improve print quality, and help the environment (eliminates caustic chemicals, significantly reduces water use in processing, and eliminates silver in discarded prints).

Dye-only (cyan) analog soundtracks REQUIRE the use of red LED sound readers. A dye-only track played with a tungsten exciter lamp will have very low signal levels and very poor signal-to-noise. Dye-only tracks will be implemented when a large majority of theatres are equipped with red LED readers. Implementation is scheduled to begin in the United States in January 2001.

Many prints in release now have "high magenta" analog soundtracks. These tracks have magenta dye + silver, and are more compatible with both tungsten and red LED readers than the previous magenta + cyan + silver tracks. "High Magenta" tracks work well on all readers, but still have silver and the problems associated with it.

The cyan dye tracks being implemented next January will NOT have silver, and will only work well with red LED analog sound readers.

Kodak's website has complete information about dye soundtracks:
http://www.kodak.com/US/en/motion/support/dyetrack.shtml

None of the three current digital sound systems require silver in the soundtrack area, as they were designed to work well with dye only. So no changes are needed for digital sound readers.

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John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com

Kodak's information on this is worth reading, but if you want a simpler description complete with some helpful graphs, go to: http://www.componentengineering.com/webdocs/whydyetracks.pdf