Re: [ARSCLIST] Preservation media WAS: Cataloguing still :-)

[Don Cox <doncox@xxxxxxxxxxxxxx>]

On 02/09/06, George Brock-Nannestad wrote:

> ----- I would like to put the term "maintaining the high quality" into
> perspective.
> 
> I have scans of photographic prints dated ca. 1920, from 5"x7" glass
> plate negatives at least. I think the original negs do not exist any
> longer. A reasonable scanner will deliver 600-1200 lines per inch -
> mine are 3600 lines per inch. 

The engravings in 19C books need about 1200 dpi for adequate
reproduction. So do pen drawings. My complaint about the Google PDF was
not that it was digital but that the quality was too low.

Here is a site that has digitised rare books at a quality that makes the
scans useful - and it needs no special software:

http://image.ox.ac.uk/


> I can see the individual grains in the
> emulsion, and I think that they are images of the original grains in
> the negatives. 

You need an electron microscope to see the individual silver crystals.
The granularity of a negative, which is resolved by a good enlarging
lens, is the statistical irregularity of distribution of the crystals.
It is the visual equivalent of tape hiss.

Resolving this does need a good scanner. What model are you using?

> This is sufficient for all purposes - one would think.
> However, everybody concerned with magnifying and printing knows that
> there is a remarkable difference between prints obtained from a light
> source in the form of an illuminated frosted glass and from a
> condenser. This is due to the way the individual grains are
> illuminated and the fact that they are actually carried in a three-
> dimensional matrix, and it influences the contrast and definition of
> the result.

Mainly because of the scattering of light.
> 
> Now, future scans may be able to make a three-dimensional mapping of
> the grains in an emulsion, and I foresee that future data processing
> may be able to provide much better possibilities for making use of
> this three-dimensional information, that is, the information content
> of a future (almost reachable today) scan is higher than a present day
> scan.
> 
> So, the term "maintaining the high quality" is entirely dependent on
> the resolution of the data capture. To the extent that it is possible
> to extract more information from the original analog medium than is
> actually extracted today, we are actually _not_ "maintaining the high
> quality" of the original. The infinite life will at all times be only
> for the data captured today, with today's resolution. This is one
> reason why it may be sensible to fight for preservation of the
> originals for as long as possible - deep freeze storage will slow down
> all chemical processes of deterioration, but it is costly. And this is
> really what it all comes to: cost. The sad thing is that we cannot use
> costly procedures for everything, so we have to make a choice. Choice
> means selection, and that means that there are things that the future
> will never be able to access, neither the original nor the resolution
> is available. However, such is life, and we must maintain that even a
> poor representation (viewed with Future's eyes) is better than no
> material at all. And we must remember that there were times where
> there was no photography, no sound recording, and no video recording.
> Writing, drawing, and painting (more expensive) was the way to
> transmit information to future generations, apart form oral tradition.
> Mass transmission was by printing.

There was a time when there was no writing, drawing or painting.
> 
> So, go out, be happy and work for open source file formats, so that
> they will be supported in the future.

Regards
-- 
Don Cox
doncox@xxxxxxxxxxxxxx