Re: Digital Film backup

[Richard Knoppow <dickburk@ix.netcom.com>]

----- Original Message ----- 
From: "Dan Haygood" <dan@haygoods.org>
To: <alt-photo-process-l@usask.ca>
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 digital
> encoding of the image.  The photograph is not latent; the 
> dye changes
> state upon direct application of high-intensity light, so 
> it doesn't need
> to be developed.  It also seems to stay that way, so it 
> doesn't need to be
> fixed.
>
> Because it's dye-based, it's probably a good idea to copy 
> the image to new
> media (i.e. make a new CD) every once in a while. 
> Fortunately, the copy
> will be exact, not suffering from generational 
> degradation.
>
> If we (as a species) can still decipher cuneiform now, 
> we'll still be able
> to decipher--with the help of a microscope--ISO9660 spiral 
> pictures of
> JPEGs for thousands of years into the future, barring 
> intermittent erasure
> of all human knowledge in nuclear (or what have you) 
> armageddons.  By
> then, the majority of historical images, however filtered 
> by various
> "social importance" filters through the eons, will have 
> been transferred
> to new encodings and new media.
>
> But, one could always store images in a less-intensive 
> simple encoding
> (say, a bit map), and hammer the data into titanium. 
> That, along with a
> Voyager-style line image of a prism and spectrum with 
> marks for R, G, and
> B, should allow the most primitive of species to recover a 
> digitized
> image.  I doubt the colorguide picture would even be 
> needed, given how
> clever we are right now.
>
> So the only issues seems to be the appreciation of the 
> image without
> decoding, and whether or not analog chemical images can 
> ever be adequately
> digitized, and what to do until then, if they can.
>
>    - Dan
   A 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.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com