RE: [Leica] OT: Archival of digital images

["Tim Atherton" <tim@KairosPhoto.com>]

It's a big subject guys and gals. I recently attended a short workshop on
this, run by some conservation scientists who are busy testing the longevity
and stability of various digital optical media.

John Poirier will probably correct my mistakes (and understand more of the
data), but while the testing is still ongoing, it seemed likely that for the
best disks, 50 - 100 years was, I think, looking like a good possibility -
we'll know better when all the data is in. That is, for Gold foil and
phthalocyanine dye (not cyanine - somewhere I have a chart of the different
dye/foil combinations), from a good manufacturer (ie generally better
quality control = better balanced disks = less read/write errors, fewer
defective foil layers etc etc.).

NO labels or writing on the disk (remeber, the TOP layer is the most easily
damage - try writing on an old one reasonably hard with a pencil! or pulling
a an old label of, along with some of the foil) - many inks may/will
introduce chemicals that can lead to breakdown/interaction over time. If you
must write on it, use a non- solvent pen and only use the clear area in the
middle. Labels have both potentially yucky glues, and also, even round
labels, introduce significant imbalances that reduce the read/write accuracy
a great amount. This means that your data has more errors, so any extra
errors introduced over time with ageing/decay will be more significant. Keep
in the jewel case( polystyrene, polypropylene or polycarbonate), on edge, no
inserts if possible (not acid free). Store in the dark.

Of course, the biggest dangers are still scratching, theft, fire, disaster
etc. Make two or three copies, store two in different places and use one for
access/regular use

And fellow luggers, I will NOT get into a debate of the science involved in
this! I you want to do that, do it on your own :)  I just attended a
workshop. These guys have already tested CD's for disaster recovery - ie,
soaking, heat damage etc, and how to deal with that. Now they are working on
Longevity. I saw bunches of data, graphs, sine waves, and had detailed
technical and mathematical explanations, but 97% goes in one ear and out the
other. I'm, just passing on the general recommendations so far!

Remeber, this is for long term archiving your stuff, not for the pile of
discs by you PC that you keep hunting through to find that picture you shot
last month.

Tim A