Re: Digital Film backup
----- Original Message ----- From: "Dan Haygood" <firstname.lastname@example.org>
Sent: Tuesday, June 12, 2007 8:44 PM
Subject: Re: Digital Film backup
An image on a (home made) CD is a dye-based spiral photograph of a digitalA couple of things: Dyes, in general, are fugitive. In particular application of strong UV light can fade many types of dyes.
However, the "image" on a CD or DVD need not be made of dye, in fact, most commercial optical discs have tiny pits which interfere with the transmission of light. The life of these discs seems to be limited mainly by the life of the reflective layer on one side. It seems to me that a lot of improvement could be made by finding better ways of protecting the deposit than are generally employed now. Also, other methods of recording a digital bit stream could be used such as your suggestion of making a CD or a noble metal. Other possibilities suggest themselves.
It is possible to have a very high degree of error immunity by using a holomorphic method of recording the data. Current methods provide a large amount of redundancy to accomplish this but, I suspect, it would be possible to make a recording which could withstand a great deal more physical damage than a CD and still be recoverable.
The problem of maintaining the recovery technology remains but the argument against digital storage because of the need for migrating the information to a new format periodically is partly specious since other forms of data storage also need periodic copying as the strorage media become degraded. Nonetheless, the fact that microfilm can be read with no more aid than a strong magnifying glass suggests such relatively simple technology should continue to have a place in a world increasingly dominated by very complex technology.
Los Angeles, CA, USA