 |
 |
A few comments. John Poirier wrote: The situation for DVDs, as Mike Richter noted, is unclear. We have used Quantegy gold dye discs, but they seem to have been discontinued. The only DVD designated as "gold dye" that I'm now able to find is made by an outfit called 'MAM-A" www.mam-a.com. They make a claim for extended longevity. Below is part of an e-mail that I received from a MAM representative in September of 2004: "Thank you for your recent inquiry. In answer to your questions, phthalocyanine dye is a dye used only in CD-R media. DVD-R media uses a different dye that we are unable to disclose at this time. We do not manufacture DVD-R using a gold reflective layer, since the reflectivity is too high for the players on the market. Only silver is used." Konrad Strauss wrote: Now for the nitty gritty. Generally speaking, cyanine dye works with a wider range of laser power and tends to be more compatible, especially with legacy burners This may have been true at lower writing speeds (1x, 2x) and a few years ago, but for the testing that I have performed on a large number of discs, I have found that most discs nowadays with phthalocyanine dye produce very low BLER rates at moderate (4x-12x) writing speeds. I don't believe this is an issue. Jerome Hartke wrote: Does anyone have solid data showing that CD's are especially sensitive to UV? I see this mentioned rather frequently, but without supporting data. CD's are sensitive to IR, since that is the wavelength used for recording. I have performed some small studies that involved exposing a variety of CD-R discs to "standard office" fluorescent light and sunlight through a window (facing east). Azo (the third dye type used with CD-Rs) and cyanine discs tended to fade and exhibit an increase in BLER. This occurred with office light exposure and sunlight. For some discs, effects of office light exposure where noticed after a few weeks (24/7 exposure). With the office light test, discs where about 6 feet from the light source and therefore, no heating effect was responsible for the fading. Phthalocyanine dye discs did not fade even with long exposures to window or room light. Joe Iraci Senior Conservation Scientist Canadian Conservation Institute