Digitization for Special Collections on Paper and Film

These standards suggest best practices for digitizing paper-based material and film/glass originals that are slated for intensive visual study. Digitization standards for these types of material prioritize legibility, artistic creation, and historical significance, requiring deep zoom and resolution of fine detail. While material digitized according to these standards may be in good condition, it may be vulnerable due to inherent vice in the medium (such as brittle paper or deterioration of a film substrate). Conservation assessment is recommended prior to digitization. The result of the assessment may determine a need for treatment before digitization, after, or both.

Paper-based Digitization standards for preservation

These are broad categories of material and encompass a large percentage of special collections, including manuscripts, bound material, a variety of flat artwork and photographs. Paper based items should be photographed or scanned to 7200 pixels on the long axis, 500 PPI, minimum, generally not to exceed 9600 pixels long. This allows for predicting long-term storage needs based on the number of items in a collection or project. There are exceptions to this, such as scrolls, where 7200-9600 is appropriate for the short axis.

Special collections captured on microform (inherently grayscale) require high resolution digitization to account for the magnification of the original document relative to its representation on film. For example, an 8.5x11-inch document, captured on 35mm microfilm represents an approximately .12 rate of magnification; 3500 x .12 = 420 (PPI). Dedicated microform scanners are required for this type of imaging.

Film-based Digitization standards for preservation

Film-based original photography requires very high capture resolution: 3000 PPI to account for fine detail in original film up to 4”x5”. Because the recommendation is a single resolution for all film sizes, resulting file sizes may be drastically different. To achieve this resolution, for smaller sized originals, high-resolution photography with lightbox illumination is possible. A more direct approach is to scan the materials, a slow process that must be accounted for when facing deadlines. The slower process to meet this specification may result in high costs when considering outsourcing this work.

For film larger than 4”x5” the recommended capture resolution is 2000 PPI. While this film has the same film grain resolution as smaller film, reasonable file sizes must be considered when accounting for long term digital storage.

Master File Format: All master files should be uncompressed, Tagged Image File Format (TIFF) version 6, in either “little endian” (IBM PC) or “big endian” (Mac) byte order. In addition, all files must pass JHOVE format validation.

Resolution: Image capture resolution is measured in pixels per inch (PPI). This should be a true optical resolution; the lens and pixel array in the capture device should be capable of creating an image file to the required resolution specification without interpolation.

Bit Depth:

Color (RGB):

• Images are captured natively in 24-bit RGB RAW or TIFF format and Master Files are exported as 24-bit TIFF files with the “Adobe RGB (1998)” color profile embedded.

Grayscale:

• Master Files are saved in 8-bit mode and should be embedded with the “Gray Gamma 2.2” profile.

Editing:

• All images should be cropped to include the entire item/object, leaving a small background border around the material to show the entirety of an object or manuscript page. Black borders are preferred but there are exceptions, such as dark originals or backgrounds used to create visual contrast and enhance legibility.

While sophisticated image viewers can easily rotate an image, the master image file should be oriented properly. For bound materials with pages of varying orientation, default to the orientation of the binding.