How long does a cd last when used as a backup for files, and what tells you that they are going bad?
I don't know if you are addressing me. But first of all, there is a difference between CD and CDR. With CD's they are manufactured by a process that embeds the data recording "pits" in metal that is then coated with plastic, and they can last a very long time unless broken or deeply scratched. CDR or recorable CD discs have a dye coating that a laser records the data in pits in the dye layer. Ordinary, inexpensive CDR disc recording may last quite awhile if stored carefully, but if exposed to very much light the dye fades and the recording becomes unreadable. There is no warning.
Almost 20 years ago Kodak was developing a scanning and recording system called Photo CD, and they had developed a CDR disk with a microscopic coating of metalic gold above and below the dye layer, which provides protection from radiation including light. Before the Photo CD service was open to the public Kodak invited some including myself to send them some 35mm film images and Kodak would scan them and put them on a Photo CD disc. I still have that gold/gold Kodak Photo CD disc and it is fully readable with my computers.
The mention of the Kodak Photo CD brought back many memories. In fact, Adobe had a Kodak Photo CD format; has long deleted it. I believe Kodak was far ahead of its time and was at a time when things were really changing in way photos were being stored. The intent was for one to have their photos developed and then had a choice of having them put onto their Photo CD along with a printout of the photos Then since the CD could hold much more than on a roll of film, one could take it back in and have additional photos stored -- up to a total of a certain amount. Then, Kodak manufactured a Photo CD player (which could also play music CDs for those who liked that also. I have one and still use it to play music CDs and show the kids one of the original interactive Photo CDs where one could do various things such as crop, zoom, burn to disk among other things. It came too fast, and disappeared as quickly. At the end Kodak designated a vendor to handle questions and final disposition of the players. Too bad -- caught in the middle of a quick changing media. I think I will keep the player till it or I die. lol As far as the life as Mr Brrooks mentioned -- what can go wrong other than it will be replaced with a new way to store -- done usually without any thohough of how the decision will affect our fellow man.
I don't think Kodak ever imagined that within three years of the introduction of Photo CD services there would be scanners on the market for a little over $2,000 with a resolution of 2700/2800dpi, When Photo CD was introduced a Nikon 2000dpi scanner cost $15,000.
Also, the Photo CD services that were licensed varied a lot in scan quality due to the fact there weren't many skilled operators available to do the work.
The Photo CD technology was very good, but the execution and management of the service was poor in comparison.
Actually the Photo CD module in Adobe was not very good at all compared to what was provided in Corel PhotoPaint. I think Corel had a much better relationship with Kodak, maybe because Corel also licensed Kodak color management.
An interesting phase in digital photography, that I agree was ahead of its time, if it ever had a time as a proprietary system.
Yes, it is almost as bad as Bell Laboratories introduction of the Picture Phone -- the government said it was not good to use telephone lines for video transmission and it would be too expensive so it died in its infancy. Today it is rampant. (these are the same people who destroyed the best communication system in the world -- too bad the company could only use the things they invented for the telephone system, which used only things made in the USA. Things that they invented along the way had to be given away or licensed for a moderate fee) - nice to have many good memories -- today is left will I have a job tomorrow. hmmm