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Author Topic: Newer Red LED's Alexander Alves Film Handler Posts: 33 From: Diwanman, Vasai, India Registered: May 2003 posted 06-25-2003 12:15 AM                     Ive seen the older Cat701 Dolby Digital Reader giving a fantastically low error rate with brand new prints.After the life of the led is over, on changing the LED the error rate does is comparatively higher. Does this mean that the newer LED's are not good or they do not have the right wavelength? Who manufactures these LEDs? And why are they coming with reverse polarity?  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-25-2003 08:31 AM                     The quality of the RED LEDs vary all over the place and always have. Some have great light output while some do not...some seem to last forever while others seems to die in a about a year or two. As to the polarity. One of the cautions was that the polarity is not consistant. I have found that all of the RED LEDs to be identically polarized to each other. Likewise, I've found all of the IR LEDs to be polarized with each other. However, I've found that IR and visible RED LEDs have been opposite to each other. Who supplies the bulk of the LEDs...why DOLBY, of course...why do you think they want the stupid things so much? It isn't because they are better, in fact they are much worse. If you want good performance from a digital reader, use white light, if you want good performance from a solar cell...use IR light, it is that simple. Dolby should have stopped with the Cat. 700 reader and the industry would have been much better for it. Steve  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 06-25-2003 09:02 AM                     Dolby has also overlooked the possibility of using a custom multiple array WHITE LED.......... I have to wonder if that wouldn't have been the best route to go for a solid state emitter. The CAT 700 was by far the best of the lot of readers out there.... Mark  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 06-25-2003 04:56 PM                     Quick question -- How exactly do errors impact the presentation in the theatre? For example: Can we hear a difference between a "1" and, say, a "3"? In terms of error rates, what is the threshold at which the system starts to sound bad or default to analog?  |  IP: Logged Carl Martin Phenomenal Film Handler Posts: 1424 From: Oakland, CA, USA Registered: Feb 2002 posted 06-25-2003 05:02 PM                        you shouldn't hear any difference until it fails. since it's digital, it works perfectly until it fails catastrophically. carl  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 06-25-2003 06:04 PM                     That's what I thought but I figured I oughtta check before I go ahead and ask something like: So what's the big deal? Why do we care if our error rate goes up? And I don't mean that as a rhetorical...I'm really just asking.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-25-2003 06:11 PM                     Mark, Dolby isn't interested in the white-light LED anymore than in the EPT lamp...neither makes them money. Come on, a $15.00US lamp that lasts over a year and is user changable...it is pretty tough to beat. By using the visible red LEDs for everything, Dolby has been able to artifically inflate the red LEDs numbers that will, no doubt, improve their cost to Dolby and possibly allow them to give false quantities regarding the red-reader conversion (by merely stating a number on LEDs manufacturered rather than ever stating the quantity that actually went to analog readers). Steve  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 06-25-2003 06:44 PM                     Steve, I wasn't thinking about Dolby's cost vs. profits, nor about EPT lamp life. I was thinking thata WHITE version of the LED array might be better noise wise. I'm quite sure it would cost a fortune to make them......figure about three times as expensive as the red is. Mark  |  IP: Logged Manny Knowles "What are these things and WHY are they BLUE???" Posts: 4247 From: Bloomington, IN, USA Registered: Feb 2002 posted 06-25-2003 11:33 PM                     So does anybody know the answer to my questions? I will re-state them... (a) What is the highest error rate tolerated by SRD before defaulting to analog? (b) At what point in the error rate number line should one become concerned about digital tracking errors?  |  IP: Logged Alexander Alves Film Handler Posts: 33 From: Diwanman, Vasai, India Registered: May 2003 posted 06-26-2003 12:01 AM                     Manny, Here in India it would be ideal to start with lowest possible error rates as films run here for maybe 10 to 15 weeks. So with print conditions getting worse with every run, we wouldnt like the processor switching to SR. Not that an error rate of 5 would sound any worse than say 3. Moral: The lower the error rate better the chances of the film running in Digital over its period of showing.  |  IP: Logged Adam Fraser Master Film Handler Posts: 499 From: Houghton Lake, MI, USA Registered: Dec 2001 posted 06-26-2003 12:10 AM                        Error rates of 7 or 8 are where we get concerned. Most new prints track 2 or 3 for us, used is usually around 5.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-26-2003 12:12 AM                     Manny, The highest error number for Dolby Digital is "8". Sonically, the difference between 0 and 8 should be zero. The higher the number, the more the error correction has to work. However, if the error correction does work, the digital word is recreated exactly as it should so sonically there is no difference. The error number is a decent indication of how well the system is reading the film. As the digital track becomes damaged, the more the error correction has to work. Also, as the reader system becomes less calibrated (focus, azimuth, light levels) so too will the error numbers increase. Generally, if you have a reader system that yields a steady 5 or better, then there isn't too much to worry about. However, if that same system that was yielding a 5 or better starts to consistantly rise over several weeks time to say 6. or 7...then there is an indication of impending failure. More often than not, the cause is LED fade or the light source going bad. Also, generally as one approaches 8 on the error meter, the number of block failures (repeated blocks) also tends to increase and they are most certainly audible. Steve  |  IP: Logged Mathew Molloy Master Film Handler Posts: 357 From: The Santa Cruz Mountains Registered: Nov 2000 posted 06-26-2003 01:07 AM                     Continual error rates of low 6's to 7 can be heard as what I refer to as 'blips' particularly during music/long tones. Of course the closer to F it gets the more those 'blips' can be heard in regular dialog.  |  IP: Logged Alexander Alves Film Handler Posts: 33 From: Diwanman, Vasai, India Registered: May 2003 posted 06-26-2003 01:13 AM                     Hey guys you'll are all missing the point. What I wanted to know is are there multiple manufacturers of the LED's under discussion. Agreed to what Steve says some LED's die in a year and some last forever. Are there no standards? USL is also manufacturing LED's but none seem to match the quality of the Dolby LED's.  |  IP: Logged Mathew Molloy Master Film Handler Posts: 357 From: The Santa Cruz Mountains Registered: Nov 2000 posted 06-26-2003 02:36 AM                     Actually, Alexander, the thread wandered. Hope someone can answer your question though.  |  IP: Logged

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