Preservation

Aerial Photo Median - 4000 Line [AEF-R1]

Record Type Aerial - Film Negatives and Positives
Expected Use Reproduction Master
Product Name Aerial Photo Median - 4000 Line [AEF-R1]
Product Purpose

The purpose of this product is to respond to reference and reproduction requests.

Nature of Source Material
  • Hard copy source images aerial film negatives and positives in any size not at risk due to deterioration or obsolescence
  • Any aerial film negatives and positives still image digital preservation master file in any size
File Properties Data Format

TIFF, version 6.0 (.tif)
Uncompressed

Capture Information

Bit Depth

  • 8-bit grayscale for B&W
    • 16-bit grayscale recommended
  • 24-bit RGB for monochrome and color
    • 48-bit RGB recommended

Pixel Array

  • 4000 pixels across the long dimension

Spatial Resolution

  • Calculate from actual image dimensions
    • Approximately 1800 ppi for 6cm x 6cm originals and ranging down to the appropriate resolution to produce the desired size for larger originals
    • Approximately 800 ppi for 4" x 5"
    • Approximately 400 ppi for 8" x 10"

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.

The image is always presented as a positive image regardless of its original polarity.

Typical file size: 8 bit grayscale: 27 MB
16 bit grayscale: 55 MB
24 bit RGB: 82 MB
48 bit RGB: 165 MB

Other Information
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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