Humanist Discussion Group, Vol. 17, No. 344.
Centre for Computing in the Humanities, King's College London
www.kcl.ac.uk/humanities/cch/humanist/
www.princeton.edu/humanist/
Submit to: humanist@princeton.edu
Date: Mon, 27 Oct 2003 06:48:08 +0000
From: "Jim Marchand" <marchand@ux1.cso.uiuc.edu>
Subject: scanning
Francois' point is well taken, but things have changed. There
was a time when ones scanner offered 150 dpi (dots per inch), but
now we have digital cameras with many megapixels. I would not
use a scanner nowadays, but rather a digital camera. With the
scanner, one has always the possibility of damaging the binding,
etc., whereas with a camera, one has the possibility of doing
filtration in real time, seeing the result before `printing',
etc. Francois' point on analog vs. digital is also good. A
digital picture is like a pointilliste painting and consists of
many separate (discrete) points, whereas one has a tendency to
look upon film as continuous. It is not at all continuous,
really, and zooming in or enlarging is likely to involve one with
`grain in the negative' (breakup of the silver salts). The Nazi
who took the photographs, if he used the best film and camera
available (say a Leica 35 mm., with Adox KB 14 film, developed to
a gamma of 7), would still have more of a grain problem than a
present-day photographer with a 6 megapixel digital camera. One
needs to keep the analogy of the pointilliste painting in mind.
Many photographs of yesteryear were printed with a half-tone
screen and (like the pictures in the Sunday newspaper) are really
dpi, as you can easily determine by magnifying them.
Were I the keeper of an archive and wanted to preserve a record
of my holdings, I would get an SLR (single lens reflex, to avoid
parallax) 6 (or more) megapixel camera (street price ca. $1000,
1K) + filters (write the camera company to see what they
recommend). With a proper stand and lighting, I would make a
digital photograph of each page, using the proper filter. Look
at the photograph before you preserve it, with the filter over
the lens; see what looks best. Record filter, time, etc. I
would keep the picture in TIFF format. {In CurrentCites 14.10
(October, 2003), Roy Tennant points out: "As anyone familiar with
the issue of digital preervation knows, the real problem facing
those in the field is migration. That is, beinging files forward
from dead file formats into formats that can be used with current
software."} TIFF is not going to die. It takes up a lot of space
in your storage, but that is no longer a problem. What the
megapixel SLR camera bring us is the ability of a total amateur
(with care) to take satisfactory archival pictures. Do not
fiddle with the result, put it in storage. If you want to use a
program to fiddle with the result, fine, but keep your first
picture in storage. Above all, do not treat your archival
pictures with non-algorithmic methods.
When you take a digital photograph, an LUT (Look-up table) is
generated, where each pixel has at least the form of f (x,y),
where x and y are the familiar geometric location (10 over, 9
down) of the pixel and f represents the gray-level, color,
whatever, the radiometric information. In general, any fiddling
with the geometric information could lead to forgery, radiometric
is ok, ceteris paribus. Every archive in the world ought to
generate a digital record of its holdings, making it available to
scholars. Let the scholars do what they will, so long as the
original is kept. Every record ought to be in TIFF, 6 megapixel
or more.
Where artifacts are concerned and 3-D photography is needed, you
are going to have to go to an expert. Field photography is
another matter. I could post a bibliography. Do we still have a
Humanist archive?
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