Scanning for preservation copy
Find typical lossles compression for scores
should last several hundred years
"Columbia University initiated an investigative project funded by the
PRESERVATION AND ACCESS. The project was to identify the most acceptable
preservation and access techniques available for oversize, colour images that included a
series of historical maps.
MicroColor International, as one of the participating vendors, decided
handle this challenging project in stages. Having carefully looked at the
merits of different storage media available today, they concluded that only
Cibachrome colour microfilm (now called Ilfochrome) offered a known
history of image stability. Data from the tests performed at the IMAGE
PERMANENCE INSTITUTE Rochester NY, had shown that this colour
microfilm has an archival dye & image stability of several hundred years.
Therefore this film material was selected for the first stage of the project.
A colour microfiche of each map was created using large-copyboard
special design 105 mm. camera, set for 'full-frame' or one-map-per-fiche
format. Microfiche was chosen because the film offers a human readable
interface, a proven archival life and very high resolution in excess of 300
lp/mm (line-pairs per millimetre)."
See test result at: http://www.microcolour.com/ilfo_test.htm
Ilford's Cibachrome Microfilm
Preservation Resources offers color microfilming options for the preservation of collections for which color rendering is critical. Preservation Resources uses Ilford's Cibachrome color microfilm, a direct positive silver dye bleach film on a polyester base. All dyes are incorporated into the film's emulsion; they are not generated during processing.
Cibachrome microfilm is capable of faithful color reproduction while achieving good resolution (132 lines per mm at 12x) and is among the most stable of color films. Tests indicate that Ilford's cibachrome color microfilm has an estimated life expectancy of approximately 300 years in dark storage without appreciable color shifting.
In the September 1992 issue of its newsletter, the Commission on Preservation and Access published a special report entitled, "Research on the Use of Color Microfilm." This report concluded that color microfilming is a viable preservation method. Even at room temperature, it is possible to preserve master color film as long as 100 years.
At Preservation Resources, color microfilming is done on a Herrmann & Kraemer camera equipped with four 3200üKelvin tungsten-halogen lamps and a Zeiss S-Biogen 40mm lens, considered one of the best lenses available.
Preservation Resources does not duplicate from the camera negative, but instead films the material once for each generation of film required. This cost-effective approach ensures a uniformly high quality product.
There are no generally accepted international standards for colour microfilm. Ilfochrome (former
Cibachrome) seems to be only type of colour microfilm with archival quality.
ISO 543:1990 Imaging materials
Photographic films - Specifications for safety film
(cf. forthcoming ISO 18906 - draft)
Silver halide film (16 mm, 35 mm, 105 mm, black and white, colour),
safety base, first generation
(or a generation accepted as replacement, sc. printing master). Production and archiving must
follow international standards to ensure indefinite access. Such film is regarded primarily as
preservation material which shall not to be used for other purposes. While films on a polyester
base may have a maximum live expectancy (LE) of 500 years, films on a cellulose-ester-type
base can have a maximum LE rating of only 100 years.
200 line pairs per mm
35mm equivalent to 140MB
120 lpmm equivalent to 3048 dpi
Here's the thing: A 35 mm slide is 36x24 mm, if mounted, is about 1.3 x 0.84 inches, so at 300 dpi, you would get no more than a
(300 x 1.3) x (300 x 0.84) = 390x252 pixel image from full frame. And twice that size with a 600 dpi scanner, I get about 780x506
pixels from mounted slides at 600 dpi. That size might be acceptable for web pages or TV, but is not sufficient pixels for printing.
If you scan 35 mm film at
600 dpi, and print it at say 200 dpi, then the image will be scaled to
print at 600/200 = 3 times larger than
the original film. If the original was 1.3x0.84 inches of film (full frame), then that is nearly 4 x 2.5 inches printed, less than drugstore
photofinisher size. If you tried to print 8x10 inches, then that 780x506 pixel scan prints at about 506 pixels / 8 inches = 62 dpi, less
than good. So this size image might be acceptable for a web site, but probably not of much interest for printing on paper. But if our
film size were 4x5 inches, the answer is different. See the FAQ section for more.
Howtek 4500 11"x11.8" 4000DPI 3.8Dmax 36bits $6,000
LT-Hell CromaGraph S 3300 17.7"x20" 9600DPI 3.9DMax $20,000
Optronics ColorGetter 3 10.5"x12" 8128DPI 36bits, 4.0DMax $7000
Screen DTS 1015AI 4"x5" 2500DPI 3.9 DMax $2500
Screen DTS 1030AI 10"x12" 5200DPI $6250
Screen DTS 1045AI 12"x17" 8000 DPI 3.9 Dmax 48 bits $12,000
Eurocore Eurocore HiScan Drum scanenr 4"x5" 10,000DPI 48 bits, 4.5Dmax $20,580
Howtek Scanmaster 35 Plus 24mmx36mm 2000DPI 36bits