Guidelines: Content Categories and Subcategories Objectives:
Reformatting Historical Printed Matter, Documents and Manuscripts,
and Pictorial Materials — Content Categories and Subcategories Table
Still Image Working Group

Use Cases: Master Images and Image Sets

• Digitizing organization uses archival or production master image(s) to produce derivative images for the use cases listed under the tab to the right.
• Digitizing organization uses the master image set (or an appropriate derivative image set) to create a virtual replica or a physical replica of the original item in the event of the loss, deterioration, or de-accessioning of the original.
• Digitizing organization (or successor/receiving agency with an archiving mission) sustains the master (or migrated copies) for the long-term without loss of essential features.
• Digitizing organization uses masters for disaster recovery in the event of impairment of digital asset management systems.

Quality Notes

• Image-quality characteristics of the archival or production master image(s) must be sufficient to support the production of the various image types listed under the Derivative Images tab. Dependencies include appropriate image specifications and a production activity that applies appropriate process controls, e.g., the use of targets to monitor output, a quality assurance process that includes the use of calibrated monitors and viewing environments, and various automated tools.
  
• An additional dependency is the quality of the source microfilm image itself, which reflects the degree to which the film in hand conforms to microfilm standards.
  
• In order to produce a virtual replica of the original item, the digital image set should include all of the elements of the original work that were imaged on the source microfilm. For some "two-up" microfilm frames (two pages per frame), the digital set will contain one image for each page (i.e., the pair within a single film frame will be represented by two separate digital images). When a virtual replica is the goal, the production process should create structural metadata for the complete work.
  
• In order to sustain or migrate the master over the long-term without loss of essential features, the following features are required: (1) image-quality characteristics as above, (2) completeness of coverage and structural metadata as above, and (3) the selection of sustainable digital-content formats.
  
• Disaster recovery in the event of the impairment of digital asset management systems depends upon the availability of metadata in standardized formats, including embedded image-level metadata and work-level descriptive, administrative, and structural metadata.
  

Use Cases: Derivative Images and Image Sets

• Patron sees or reads inline image or image set in user interface. In some cases, users will seek viewing access to a complete work, in effect a virtual replica.
• Patron makes a hard copy of one or more images for personal use. In some cases, patron requires a print-on-demand copy of a complete work, in effect a physical replica, albeit in this case (scans from microfilm) a replica with moderate print quality.
  
• Patron is confident that the content received is an accurate and/or authentic reproduction of the original item.
• Patron (or content delivery system) receives information on rights and restrictions (delivery system may act on that information, if appropriate).
• Patron downloads one or more of the derivative images and, later, uses embedded metadata to identify the content and to determined technical and provenance information about the image.
• Patron examines the entire online image-set or a hard copy of the complete work (e.g., a book), to visualize it "as originally published."
• In some cases, digitizing organization runs OCR process to produce text. Patrons may read, search, or download this text for a variety of uses.
• Publisher uses image to illustrate a book.
• Broadcaster uses image in television program.

Quality Notes

Inline image in user interface:

• Text is legible and graphic illustration content is reasonably clear. Zoom in may be required. In rare cases, legibility may depend upon contrast stretching.

Hard copy output:

• Equivalent to good quality photocopy.

Patron confidence in accuracy and/or authenticity:

• Depends upon provenance metadata (attribute of the copy) and trustworthiness of the provider (attribute of the institution).

Images for OCR processing:

• Produce text at a reasonable level of accuracy.

Image used for book illustration:

• Considering the source, images destined for use in the creation of printing plates should be as good as possible.

Image for use in a television program:

• Considering the source, images destined for use in the creation of television programs should be as good as possible.

Note: Derivative images will generally be in an output-referred image state.

Recommended

Comments from NARA Guidelines, p. 45.

When scanning microfilm, often the desire is to produce images with legible text. Due to photographic limitations of microfilm and the variable quality of older microfilm, it may not be possible to produce what would normally be considered reproduction quality image files. Your scanning approach may vary from the recommendations cited here for textual records and may be more focused on creating digital images with reasonable legibility.

For B&W microfilm, scanner software should be used to match the tonal scale of the digital image to the density range of the specific negative or positive microfilm being scanned. Example: the minimum density of negative microfilm placed at a maximum % black value of 97% and the high density placed at a minimum % black value of 3%.