Ken Durling wrote:
Not magnetic tapes - the adhesive that holds the particles to the
substrate deteriorates in 15 years or so. I know this from bitter
experience. It also matters greatly if the tapes are stored head or
tail out. The print-through resulting from long-term storage head out
can obliterate material on neighboring layers. Cassettes - well they
don't last long at all.
There have been library archive studies that have put a similar short
life on CD's, and even less on DVDs - the laminate
deteriorates. Obviously again, storage conditions make all the
difference, just with like photographs.
Ken
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Hi Ken,
I agree with you but at the same time have cassettes I recorded 25 years
ago that still play today. Yes, I do understand print through and with
magnetic tapes that is a factor but this too varies depending on the
materials used to make the tape, Chromium Oxide, Ferric Oxide, etc.
DVDs and CDs will last longer but the key there as you noted is storage.
Much like Ektachrome slides, light destroys CDs/DVDs. The trick is to
burn your media at the slowest rate to ensure a better deeper burn (I do
mine at 1x) and then store them in black sleeved binder and put them in
a closet somewhere. Do this and they will last 25 years or more with no
deterioration. By that time we will have replaced them with some other
media anyway. :-)
Peter K
Speed of burn per se is not the issue; best is usally 1/2 or 1/4 the
maximum speed of the drive. No further gains are achieved by going
slower.
Media is all important. The best generally available CD's are the
gold CD's by Mitsui. This is the company that licensed the gold Kodak
discs while they were still available. They are by far the longest
lasting. DVD's are not yet of that longevity, although they are
getting better. Mitsui also sells some of the best.
I have quite a few CD's from the mid to late 90's that are no longer
readable, even though recorded at slow speeds and even though
properly stored in dark conditions. The media just didn't last. A
couple of years ago I set 5 types of media out on my desk, which is
exposed to a north facing window. Within one week the Memorex and
Maxell disks were not longer readable. The Fuji was gone by 4 weeks.
The TDK lasted about 6 weeks. The Misui disk was fine after 6mo and
then I stopped. Please note that these tests are only valid for my
conditions and the particular media I was using; I know that many
brands come from various manufacturers and plants and vary greatly.
Tapes are basically good for medium term storage. Print-through is
not as much of an issue any more, and binders are better, but
physical damage such as tape warp is still a problem, and since the
information density is much higher now with tapes such as DLT4, even
minute imperfections can ruin the data.
The best solution at this time is multiple hard drives. My most
recent data including photos is on-line, and is backed up regularly
to another drive, which is off-line unless being backed up to. As I
shoot RAW mostly, another drive is regularly attached which gets the
DNG converted files. When a drive is full and no longer needed
regularly on-line, I make a complete set of DVD's and take the
duplicate hard drive off-site. So I wind up with one hard drive with
DNG files and one hard drive with the RAW files and the DVD's on
site, and one hard drive with the RAW files off-site. The only drive
that stays in an enclosure is the one with the RAW files that I use
locally.
A number of people I trust have recommended this approach, and feel
that at present off-line hard drives provide some of the most
reliable long-term storage, and there is also the advantage that
migration to larger drives/new media will be as fast and painless as
possible.
I still have the means to read pretty much any file that I have
created on my Macs since 1984. I can still read floppies and use a
nice translation program called Maclink Plus, but this will fade, so
I regularly try to bring data forward. My written files are all fully
accessible and I've used the same e-mail program since 1990. I've a
little program called Canopener that will let me get at text and
images in pretty much any file.
I'm hoping that jpeg, tiff and DNG will be supported for quite a
while, otherwise I'll have to do some more conversion.
Digital just requires a lot more vigilance and effort to stay on top
of your files, whether images or other, than film and paper did.
--
* Henning J. Wulff
/|\ Wulff Photography & Design
/###\ mailto:[EMAIL PROTECTED]
|[ ]| http://www.archiphoto.com
*
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