Re: [photo-3d] CD-Rs = 200 years?

[Tom Deering <photo-3d@xxxxxxxxxxx>]

1. Accelerated testing is all anyone can do, unless you want to wait 
200 years for your results.

2. Yes, the disks need to be stored carefully.  Slides, too.  Most of 
us have basements that are dark, cool, and dry.

3. The comparison to ink fading is not useful. Digital data is 
objectively good or it's not, regardless of who tests.  Fading is 
subjective.

4. "hardly a disinterested 3rd party"?  What FAQ author on any 
subject is not interested in the subject of the FAQ?  Why would they 
bother?

5. My sources do not quote references, but contradictory references 
have not been presented, either.  I did not find "CD" on any web page 
at http://www.wilhelm-research.com

6. Let's be practical. Even if the actual life is half the published 
amount, a CD-R may be around long after the photographer is 
forgotten.  How many of us can name one relative that lived 100 years 
ago?

If your great-grandchildren haven't discovered your CD-R and 
transferred it's contents to their wrist Cray, their progeny probably 
won't remember you or care.

Cheerfully,

Tom



On 6/18/00, Brian Reynolds wrote:
>Tom Deering wrote:
>> On 6/17/00, Andy Beals wrote:
>> >> I'm concerned that there isn't a digital storage medium
>> >> currently available that will safely retain images for the
>> >> long term.  I believe CDRs are supposed to be good for about
>> >> 12 years if stored in ideal conditions.
>> >
>> >I think you're off by a factor of ten, there.
>> How long is the life span of a CD-R?
>>
>> The life span of a recordable disc depends on several things:
>>
>> 1.   Color of disc: most makers of CD-recordable discs claim that the
>> green (cyanine) discs last up to 75 years, gold (phthalocyanine) last
>> up to 100 years and the silver-blue platinum last up to 200 years.
>> See the manufacturer's information.
>>
>
>There are a few things to take into account with these numbers.
>First, they were reached with accelerated testing procedures.  If the
>testing procedures do not actually match real world conditions
>(perhaps they for got some factor, or the conditions the test
>simulates change over the time span they are projecting) the results
>aren't good.
>
>These numbers should be taken as an upper limit, not as the average.
>
>> 2.   Environmental factors: the lifetime of the disc may be reduced
>> if is exposed to water, sun, or heat. Treating your recording media
>> carefully will extend its life expectancy.
>>
>
>This is the biggest factor.  Most of these test are reported for
>environmental conditions used by museums and archives.  That means
>storage at a controlled (low) temperature and relative humidity in the
>dark.  Almost no users of any of these products (film, paper, inks,
>and other media) will store their work under these conditions.
>
>It is possible to interpret the test data for other storage
>environments, but generally the people who pay for, or perform, these
>test are not willing to release the data.  (Remember "120 years before
>noticeable fading when stored at 50 degree F, 50% relative humidity
>and less than 400lux" is an interpretation of the data, not the data
>itself.)
>
>> Above from http://burningcd.com/faqs.html#span
>>
>
>These are hardly a disinterested third-party, and they do not cite
>there references.
>
>I would not trust the testing done by a manufacturer.  Testing needs
>to be done by a third-party in order to ensure that the results
>haven't been fudged.  Wilhelm Imaging Research
><URL:http://www.wilhelm-research.com/index.htm> has done independent
>testing for several manufacturers, and there are a few archives that
>also do testing.
>
>This has been thourghly discussed on the epson-inkjet
>
>--
>Brian Reynolds                  | "Dee Dee!  Don't touch that button!"
>reynolds@xxxxxxxxx              | "Oooh!"
>http://www.panix.com/~reynolds  |    -- Dexter and Dee Dee
>NAR# 54438                      |       "Dexter's Laboratory"

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