Digital Media Archive/Digitization Standards draft 8/23/01
|
media type |
scanner |
tonality |
resolution |
archive file |
screen presentation |
notes |
|
§ black and white text documents |
flatbed scanner |
1-bit or bitonal1 |
300-400 dpi (PDF) |
uncompressed TIFF |
|
guideline used for UIC Chancellor’s Notices |
|
§ modern printed books without illustrations line art which has little or no shading. |
flatbed scanner |
1-bit or bitonal |
600 dpi |
uncompressed TIFF |
GIF, 4-bit, 120-200 dpi |
|
|
§ black and white photographs § half-tone illustrations § other types of continuous tone illustrations § handwritten and typescript manuscript and archival materials which are nominally black and white but which actually contain shading and varieties of ink density and paper tonality. The older the document, the more likely that color rather than gray-scale may be appropriate. |
flatbed scanner |
8-bit gray-scale2 |
300 dpi for handwritten documents, typescripts, half-tones 300 dpi or higher for black-and-white photographs |
uncompressed TIFF |
JPEG 640x840 for quick delivery 1040x768 or 1280x1024 for larger presentation thumbnail: 4-bit grayscale, GIF compression or JPEG |
|
media type |
scanner |
tonality |
resolution |
archive file |
screen presentation |
notes |
|
§ sepia-tone or gold salt based photoprocesses |
flatbed scanner |
16-bit color |
uncompressed TIFF |
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|
§ any materials with color which should be maintained for historical or esthetic reasons or because the color conveys information |
flatbed scanner |
24-bit color3 |
300 dpi for color photographs; spatial resolution should be 3,000 ppi on long side or 5,000 ppi on long side for photographs with critical detail. 200 dpi for printed maps and posters. 600 dpi for historical artifacts with extremely fine details |
uncompressed TIFF |
quick delivery: JPEG 640x840 for larger presentation1040x768 or 1280x1024 thumbnail: 8-bit color, GIF compression or JPEG |
For color photographs, use automatic color and contrast balance on scanner software: this will be a known bias for all files scanned on the same machine. Use color reference strip on the margin of each image. Image processing (including sharpening, blurring, histogram, threshholding, dithering, tonal contals) may be necessary. |
|
media type |
scanner |
tonality |
resolution |
archive file |
screen presentation |
notes |
|
§ high quality "art" color photographs |
flatbed scanner |
30-bit color |
600 dpi |
uncompressed TIFF |
quick delivery: JPEG 640x840 for larger presentation1040x768 or 1280x1024 thumbnail: 8-bit color, GIF compression or JPEG |
|
media type |
scanner |
tonality |
resolution |
archive file |
screen presentation |
notes |
|
§ photographic negatives, 1 x 1 slide or 35mm film |
slide scanner |
24-bit color |
2048x3072 |
uncompressed TIFF |
quick delivery: JPEG 640x840 for larger presentation1040x768 or 1280x1024 |
Pathology Dept. scans are not archived as uncompressed TIFF (there is no longer-term preservation need) |
|
§ photographic negatives, large format |
slide scanner |
24-bit color |
4096x6144 |
uncompressed TIFF |
quick delivery: JPEG 640x840 for larger presentation1040x768 or 1280x1024 |
|
|
§ 3-dimensional objects |
digital camera |
24-bit color |
TIFF |
JPEG |
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|
§ film/video |
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§ sound recordings |
1 A 1-bit pixel has two possible values, black or white. The scanned image has no shading or gray. 1-bit or bi-tonal scanning produces the smallest file.
2 Provides 256 shades of gray ranging from pure white to pure black.
3 Provides a tonal range of about 16 million different colors. Color scanning produces quite large files.
RECORD SCANNING INFORMATION:
§ title or image ID
§ resolution
§ compression
§ dimensions
§ file format
§ software
§ scanner manufacture/model
§ can date
§ scanner operator
DATA BACK-UPS:
access files -- online, backed up by ACCC
masters --offline (CD) and offsite
EQUIPMENT AND SOFTWARE
Scanners should be capable of producing high resolution output with good color quality and few, if any artifacts ("noise" introduced by the scanning process itself. For optical character recognition, scanners with 600x600 resolution (600 pixels on the vertical axis and 600 pixels on the horizontal axis) will generally be sufficient. For image scanning, in general, the higher the resolution ability of the scanner, the closer your image reproduction original will be to the original; the tradeoff for this is a dramatic increase in the file size. Sizes of 25MB and higher may not be uncommon and should be expected.
Current equipment in the Infotech Arcades consists of: (1) flatbed scanners with resolutions of 600x600 and 1600x1600; (2) newer slide/negative scanners with resolutions of 3600x3600 and older slide/negative scanners with resolutions of 600x600; (3) digital cameras with resolutions ranging from 1.5 to 3.1 million pixels.
Note that there are restrictions to the standards as noted above, currently dictated by software and hardware.
1) The software currently used by the library for optical character recognition is Adobe Acrobat Capture (version 2.01 preferred to 3.0 due to ease of use and smaller file sizes produced). For pure text originals of black text on white paper, Acrobat Capture does not allow higher than 200dpi (dots per inch) scanning. For full color originals, Acrobat Capture does not allow higher than 400-600 dpi.
2) Many software packages cannot load or manipulate images with bit-depth greater than 24 bits; while 30-36 bits is ideal for image reproduction, it is possible that scanning at that level will leave us unable to work with the resulting images. Whenever possible, images scanned at 30-36 bit color depth should also be rescanned at 24-bit color depth so that we have multiple masters to work with. Both 36 and 24 bit images can be used as archival masters.