Use | Original | Resolution | Bit Depth |
Color Space |
Dimen- sions |
Editing/ Processing |
File Format/ Compression | Storage | |
---|---|---|---|---|---|---|---|---|---|
Archival |
Long-term archive |
b&w/text - in good-condition (high-contrast) |
300 ppi |
8-bit |
grayscale 1 |
Varies (100% of original; no less than 4,000 pixels on LS) |
Check grayscale factors 2 |
TIFF, with little endian (IBM PC) Byte Order; no compression |
|
b&w/text: to be OCR'd |
400 ppi |
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b&w/text - in poor condition, tiny print, or with illustr. |
600 ppi |
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with color |
24-bit |
RGB |
|||||||
Working |
-To create derivatives. -Publication printing. |
Same as AM |
Same as AM |
Same as AM |
Same as AM, but sRGB if color |
-Change file format.4 -Saved as sRGB -Tone & color adjusted -Sharpened |
Same as AM, but may be compressed with LZW compression if saving storage space is essential. |
If kept, same as AM. |
|
Static |
Internet delivery (multiple files) |
N/A |
24-bit |
sRGB |
No less than 640 pixels on wide |
-Reduced dimensions |
GIF6 (JPEG, medium quality, 5-7, of 10) |
||
-b&w text may be converted to grayscale/ bitonal. |
ITU/CCITTGroup IV compression |
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Compound |
Continuous reading (one file) |
? |
? |
Append all pages |
PDF or PDF/A with minimal compression |
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Tran- |
Keyword searching |
Uses Working Master |
N/A |
N/A |
N/A |
N/A |
OCR; |
UTF-8; TXT (or XML if encoded) |
Note: No color or grayscale color profile target needs to be scanned with typed (or type set) textual materials, however, such textual materials with illustrations are scanned as 8-bit grayscale and should be scanned with a grayscale target.
[1] Black and white text documents on white backgrounds should be scanned at 300 ppi, 8-bit grayscale to produce the Archival Original version, however, if the original material was a clean, high-contrast black and white printed document (e.g. laser printed or typeset) and a small delivery file is desired, the Working Master can be converted from to 1-bit bitonal and saved as the Static Delivery File. Moreover, many textual images can be reduced by as much as 50% from the size of the original material without reducing legibility. Only testing will tell for sure.
[2] Grayscale factors: minimum number of visible steps: 18; minimum number of f-stops: 5.5; Y channel noise: <=5%.
[3] Color accuracy: DeltaE < 8, ICC Profile (decrease if image is very large).
[4] If you are using Photoshop to edit the Working Master, change the file's TIFF format to PSD, Photoshop's native file format, which allows for more editing functionality.
[5] 150 dpi is a rather conservative setting for getting a reasonably good print out of most images that will fit on a computer screen. If you change the value in the Resolution box to another dpi (in Photoshop), always readjust the Pixel Dimension appropriately because changing the dpi automatically changes the Pixel Dimensions as well.
[6] Although GIF files tend to be larger than JPEG files, trey display faster in a browser because of their lower bit depth and because if their type of compression decompressed faster. Also, the GIF format is well suited to storing images of discrete data such as printed or typed text and line art.