Preservation

Aerial Photo Maximum - 8000 Line [AEF-P2]

Record Type Aerial - Film Negatives and Positives
Expected Use Preservation Master
Product Name Aerial Photo Maximum - 8000 Line [AEF-P2]
Product Purpose

The purpose of this product is to mitigate risk for loss of information and fulfill researcher/user expectations and requests. This file is at an appropriate quality level to substitute for the original record if the original record copy is no longer viable.

Nature of Source Material

Aerial film negatives and positives (B&W, color, and monochrome) with a size range of 127mm wide roll film/4x5 and up to and including 5x7 sheet film (square area equal to 10 square inches and up to 35 square inches) where there is a need to ensure that all significant visual information is carried forward.

File Properties Data Format

TIFF, version 6.0 (.tif)
Uncompressed

Capture Information

Bit Depth

  • 16-bit grayscale for B&W
    • 8-bit grayscale optional
  • 48-bit RGB for monochrome and color (default for all negatives including B&W, grayscale, monochrome and color)
    • 24-bit RGB optional

Pixel Array

  • 8000 pixels across the long dimension

Spatial Resolution

  • Calculate from actual image dimensions
    • Approximately 1600 ppi for 4" x 5"
    • Ranging down to approximately 1100 ppi for 5" x 7"

Dimensions

  • Images should be consistent dimensionally in both the horizontal and vertical directions. Overall dimensions of images should be accurate within 1/100 of an inch or .245mm of the original's size.

Tonal orientation

  • Tonal orientation is maintained so that a positive image remains a positive image and a negative image remains a negative image.

Typical file size: 16 bit grayscale: 98 MB
48 bit RGB: 293 MB

Other Information

The Photographic Imaging, Microfilm and Textual Preservation Lab uses 48-bit RGB as the default for all negatives, including B&W, monochrome, and color, when creating preservation master files. The NARA 2004 Technical Guidelines and FADGI 2010 Technical Guidelines discuss approaches for the creation of production master files, rather than preservation masters, and do not set a default for higher bit-depth. NARA 2004 and FADGI 2010 suggest that 8-bit grayscale and 24-bit color files may be created from 16-bit grayscale and 48-bit color files.

Quality Control Quality Assurance and Quality Control for Digital Imaging Products

The Digitization Services Branch’s Quality Assurance and Quality Control (QA/QA) program is evolving as new tools and resources are acquired and implemented. We are moving towards more automated and integrated systems to assure the products we make meet the specifications outlined. Digital products created by the Digitization Services Branch are validated against standardized format specifications and signature files when possible. We use a variety of format specific batch evaluation and validation tools both open source and vendor supplied, to assure technical quality level specifications are met. All files, but especially distribution system specific files, are inspected for successful playback in a variety of tools and environments. Additional quality control workflows are in development.

Equipment/System Evaluation
NARA implements scheduled service and calibration protocols according to manufacturer recommendations as well as on an "as needed" basis.

Metadata
Embedded metadata: NARA is working on embedded metadata guidelines for all file types.
Technical metadata: NARA is finalizing technical metadata schemas for all file types.

Customer Level Evaluation / Order Completeness

NARA is developing an in house job tracking order system to better coordinate work at the Branch level.

Item Level Evaluation: Automated File Characteristics Analysis
Fixity: NARA is evaluating workflows to create and validate checksums for each digital file.

For additional QC protocols for products created on the Zeutschel Camera System, please see Quality Assurance and Quality Control for Digital Products Created on the Zeutschel Camera Systems

Rationale

While the capture process for most original photograph, text-based and object/artifact original source material record types is file-based and results in digital products, there are limited options for hard copy outputs. The first is aerial photonegative prints. While digital capture specifications are established for aerial photo negatives and film positives, this workflow remains an analog-to-analog film duplication process at this time. The lab expects to transition to analog-to-digital workflow in the future. A second area is microfilm. Polyester-based silver gelatin microfilm is generated from digital preservation master files for text and cartographic collections captured in the Photographic Imaging, Microfilm and Textual Preservation Lab and then stored off-site in a climate controlled limited access vault. In addition, polyester-based silver gelatin microfilm copies are available for the Microfilm Publications beginning with the M, P. C or T prefix. Third, there is a very limited option to produce facsimile prints from digital files for specifically identified purposes only.

Currently, the digital distribution copy options are generally the same for all still images regardless of the format of the original source material.

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