The choice to create duplicate copies of collection material is often made for both preservation and access considerations. For some media, such as audiovisual materials, digitization is preservation. For fragile or actively deteriorating paper and photographic collections, a digital surrogate can be made to preserve the content and provide a stable copy for research.
Preservation Photocopying
Electrostatic copy machines that adhere to specific standards can be used to create long-lasting replacement copies of deteriorating or damaged printed materials. Creating stable copies can not only capture the information on the deteriorating original documents, but also be used by researchers in place of fragile or valuable items.
Common materials found within the Archives that will undergo preservation photocopying include newspaper clippings, Mimeograph™ or Thermofax™ copies, and fading historic documents on poor-quality paper. Valuable documents or frequently handled documents may also be replaced in folders with a high-quality photocopy while the original is stored in a separate location. This protects the original from both excessive handling and the risk of theft.
Paper facsimiles can be made by placing the paper record on the flatbed, aligning it appropriately, and copying onto 20 lb. bond paper that meets archival specifications. Original documents are retained after photocopying. An exception is made for some newspaper clippings; if they do not contain handwritten notes, the Archives discards the clippings.
The longevity and stability of the copy is dependent on the use of stable toner, the proper fusing of the toner onto the paper, the use of appropriate paper stock, and suitable storage and handling of the copy. Testing of preservation photocopy can be performed using the “peel test”. Please our case study on the failures of photocopying pertaining to cultural heritage collections here:
Still Image Digital Reproduction
Still image digitization is a core function of the Archives. Adhering to international standards and best practices for digitization, such as the Federal Digitization Guidelines Initiative (FADGI), the Archives produces high quality archival digital images to provide access to researchers, scholars, and the public. The following digitization standards are used when digitizing still images, such as documents, books, photographs, and negatives:
- Resolution
- 6,000 pixels on the long axis of the image
- Minimum value is 600 ppi (pixels per inch), increasing resolution in intervals of 25 ppi as necessary to achieve a minimum of 6,000 pixels along the long axis.
- For images from microfilm, a resolution of 300 ppi grayscale is acceptable.
- Digital File Format
- Tagged Image File Format (TIFF) using Windows (PC) byte orientation
- For color images, a 24 bit RGB setting is used, yielding 8 bits per color channel.
- For black and white images, a 24 bit RGB setting is used.
- File Compression
- None
- Metadata
- Best practice guidelines are developed and maintained by the Digital Asset Management System (DAMS) Team.
- Embedded fields follow the International Press Telecommunications Council (IPTC) Core standard.
- Mandatory embedded elements for images: Document Title, Copyright Notice, Source, and Creator.
Analog Audiovisual Media Preservation
Due to aging media and playback equipment, in many cases, digitization is the only method of preservation for analog audiovisual materials. Adhering to international standards and best practices for digitization, such as the Federal Agency Digitization Guidelines Initiative (FADGI), the Archives produces high quality preservation files, as well as production and reference quality files to provide access to the researchers and the public. The following digitization and physical care standards are followed with each media type.
Audio
- In-house capabilities
- Digital audio tape (DAT), Compact audio cassette
- Digital File Format
- Analog source: Broadcast Wave File (BWF), uncompressed and 24-bit depth, 96 kHz is preferred
- Digital source: Broadcast Wave File (BWF), uncompressed and 16-bit depth, 48 or 44.1 kHz is preferred
- Metadata
- Fields embedded according to FADGI Guidelines
Video
When videotapes are accessioned into the Archives, tape record tabs and buttons are removed or depressed to ensure the tape cannot be recorded over. The tapes are then stored in their original cases if there is no damage to the case. If cases are damaged, they are replaced with inert polypropylene cases.
- In-house capabilities
- VHS, S-VHS, Betamax, Betacam, Betacam SP, Digital Betacam, U-matic, U-matic SP, DVCPro, DVCam, MiniDV
- Digital File Format
- For Preservation: FFv1 with lossless compression in a Matroska wrapper (.mkv)
- For Production Uses: MPEG-2 in a 4:2:2 format
- For Access: H.264 in a MOV wrapper
- Metadata
- Currently, we do not embed metadata into our video files, However, an XML file containing descriptive and technical metadata is generated for, and kept with, the MKV file
Motion Picture Film
Films are wound onto 3-inch polypropylene cores and rehoused in archival film cans when accessioned. Molecular sieves are placed within the can to absorb acid vapors and regulate temperature and humidity to extend the life of the dye images and film supports. Film cans are stored flat on shelves or in archival boxes.
The Archives does not currently have the capability to reformat motion picture film in house, but follows FADGI guidelines when sending materials out to vendors for reformatting.