Digital BW, The Print

I don't know exactly with what kind of burner your wife did the DVD's but... with an exoensive trip like the one she had, I would go for CD first. Gold Archival ones. Even with a slow bandwith, she should have tried to do the backups so to preserve the images.

Second I would not rely only on CD's or DVD's  alone (you're right, sometimes they fade - but gold ones do better); better still, never leave home without some external devices - be it  a computer, USB keys or portable hard disks.

I've beeen taking pictures for thirty years now (digital and non-digital - scanned ones too) and, crossing my fingers, never had a problem. One copy on regular DVD for cheap back-up, gold CD's (DVD's are a bit too soft) and most importantly on external hard drives (firing them up once a month to keep them in shape and be assured that they still hold the data).

My collection of CD's, DVD's is still readable; when new ways of doing secure backups arrive, I will be transferring everything.

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "kwalsh74" <kwalsh74@...> wrote:
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> I haven't because I've refused to use them for any long term data retention.  I know they are a disaster waiting to happen for that application.
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> My wife has directly experienced this, to great loss.  She and a collaborator did an expensive observing run in Chile.  Bandwidth was low from the observatory, so they used DVD media to bring it home.  They burned two separate DVDs and checked both copies were functional.  Some of the data was copied over back at home for analysis, the rest of the observing run left on the disk and put on the shelf.  About six months later they wanted to reduce the rest of the data.  Gone, from both DVDs.  Sent out to expensive recovery services.  No luck, the dye had faded.  They had to re-observe those targets the following year, and time on telescopes of this size is rare and difficult to get.
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> The largest problem with CD/DVD and image files is that it is a pain to migrate the data.  Digital data that you care about should be migrated and refreshed every few years.  With hard drives this takes a few minutes, unattended.  With disks you have to slowly migrate them all.
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> As others pointed out, there is media which *should* be better.  But only if your drive burns the CD/DVD properly.  The integrity of the data is based not just on the material of the disk and the dye, but also on the dye being properly exposed and fixed by the drive.  Take a 300 yr disk and put in a drive not functioning properly and you'll get a disk that will fade in just a few months.  How will you know?  You won't, until you go back for your data and it is gone.
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> Multiple copies, multiple locations, migrated with reasonable frequency.  CD/DVD is just a poor format for implementing that...
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> Ken
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