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This topic comprises 6 pages: 1 2 3 4 5 6
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Topic: LED readers
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Jim Alexander
Film Handler
Posts: 71
From: Greenwood, Nova Scotia, Canada
Registered: Nov 1999
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posted 02-25-2003 02:59 PM
I have followed this discussion in this and many other threads and in the begining I was quite concerned. Contrary to what Gordon says that if you can't afford the $900.00 per projector, maybe shouldn't be in the business, things in a single screen enviroment are a little different. Like many rural locations, single screens are the norm where we are. And with mutiplexes moving in, our share of the market is dwindling. As such, the prospect of putting out $900.00 per projector (especially when you are running a change over system) can be quite intimidating. Its not whether or not you can afford it, but whether or not this investment, at this time, is the best choice. Since I first came across this topic almost four years ago, experts (arm chair and actual) have been saying the conversion will be in 3 to 6 months. Well it is now four years later and we are still running high magenta tracks. Myself, I convered last summer to LED and have been quite pleased with the results, but if I could have put it off for another six months I would have.
According to the Motion Picture Theatre Association of Canada, 80% of theatres in Canada are converted over to LED. That may be true across the country, but not in Newfoundland, nor with the independants in Atlantic Canada. Most are waiting until there is a firm date for conversion and when that is announced they will convert.
All I can say in all this rambling is that if the industry is going to convert, then pick a date and convert. Just stop this $&@# about starting in six months and then doing nothing. False claims like this are only frustrating independants into thinking when it comes is when I will convert. My fear is that will be too late.
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John Pytlak
Film God
Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000
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posted 02-26-2003 05:57 AM
Steve wrote:
quote:
PS...anyone that thinks I have a dislike or disrespect for Mr. Pytlak is very wrong. We definately have differing opinons on some subjects though...cyan vs. quality happens to be one of them
PS...anyone that thinks I have a dislike or disrespect for Mr. Guttag is very wrong. We definitely have differing opinons on some subjects though...SILVER vs. quality happens to be one of them.
Yes, slightly lower signal-to-noise is an issue. But IMHO, this is far outweighed by the advantages of less waste, less water usage, elimination of hazardous chemicals, more efficient recovery of silver from the film, and better picture quality (no silver soundtrack bleeding/blotches/streaks). Almost EVERYONE, including Steve, agrees that modern LED-based reverse scan readers offer a significant improvement in sound quality over old tungsten lamp readers:
As Steve wrote:
quote:
Of all of our visible red reader installations, all were sold based on the reverse-scan reader QUALITY and/or due to a Dolby Digital upgrade...
I hope that someday Steve will "see the light" --- since you can't do that with infrared LEDs. ![[Wink]](wink.gif)
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John Pytlak
Film God
Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000
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posted 02-26-2003 10:02 AM
Steve Kraus wrote:
quote:
I also note that there now exist white LED's, UV LED's...they seem to cover the spectrum. So one presumes it would be possible to have an LED that emits across the IR and visible red spectrum. Such a device would seem to be the optimum light source, able to read cyan tracks as well as silver redeveloped tracks with the extra S/N they offer.
Actually, a broad spectrum ("white") LED would not be optimum for a cyan dye track. The sharpest and most grain-free layers in color print film are the cyan and magenta. Even in "traditional" analog soundtracks, the yellow layer was NOT used because it has larger grains and is at the bottom of the emulsion pack.
Here is the spectral dye density curve of Kodak VISION Color Print Film 2383:
Spectral Dye Densities 2383
A pure color LED that has most of its light output at the peak of either cyan or magenta dye will give the best signal from a dye track. A reader with a broad spectrum LED will "see" the unmodulated light coming through between the cyan and magenta dye peaks, reducing signal-to-noise. And since there is little infrared dye density, any IR energy will not be modulated by the dyes, reducing signal-to-noise. Because high-output 660nm red LEDs have established themselves in modern reader design, the cyan dye is the best choice for a dye-only track.
Component Engineering has a very complete technical discussion:
Component Engineering: Why Dye Tracks
It's very difficult to filter a tungsten light source to a pure "red" color (around 660nm). Dye filters will quickly fade, and dichroic filters would be expensive. Even with a red dichroic filter, most of the tungsten lamp's energy would be unused, adding to the heat issues and giving poor light output.
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