Best Practices for Imaging of Text and Graphics
This is not policy, but rather a guiding document. For various reasons, projects might not be able to fulfill these recommendations. At present, technical debt related to storage and access systems makes these recommendations difficult to fulfill.
These specifications remain aspirational, but serious efforts should be made to adhere to them to better ensure the long-term preservation and usability of digitized texts and graphics.
Documents and manuscripts (unbound)
Format | Pixels Per Inch (PPI) | Bit Depth |
---|---|---|
TIFF, PDF/A | 300 or 400 PPI | 8 or 16 bits |
Modern textual documents, those printed on office paper, may be imaged at 300 PPI.
Newspapers and Serials/periodicals
Format | Pixels Per Inch (PPI) | Bit Depth |
---|---|---|
TIFF, PDF/A | 300 or 400 PPI | 8 |
Oversized Documents: Maps, Posters, Broadsides, ect.
Format | Pixels Per Inch (PPI) | Bit Depth |
---|---|---|
TIFF | 400 PPI | 8 or 16 bits |
Over-sized materials larger than 34 x 24 inches will need to be stitched together as a composite image. Each individual image should be retained as a master file. A service master may be created to represent the composite from which access copies can be derived.
Prints and Photographs
Format | Pixels Per Inch (PPI) | Bit Depth | Color Mode |
---|---|---|---|
TIFF | 400-600 PPI | 8 or 16 bits | Adobe RGB |
Photographic Transparencies
Format | Pixels Per Inch (PPI) | Bit Depth | Color Mode |
---|---|---|---|
TIFF | 2000, 3000, or 4000 PPI | 8 or 16 bits | Adobe RGB |
Recommendations for photographic transparencies is dependent on goal of digitization. It may be appropriate to scan transparencies at lower PPI to prioritize access over costs. Transparencies can also be grouped together as another means of cost-saving.