Genealogy: Scanning recommendations by image type

Genealogy: Scanning recommendations by image typeBy Barry J. Ewell

As you preserve your family history, you come across a variety of image types (e.g., documents, maps, and photographs) each requiring thought and consideration about its preservation and digitization.  Each image will have multiple uses and needs to be planned for.

Master files (sometimes called archival files) are the source files for all other digital files and ensure the long-term usability of the digital information. Master files should be saved in TIFF file format—they should not be compressed, altered or resized. Master files should be stored on a stable medium and should remain in a controlled environment.

Sharing/Access files are for day-to-day use. They may be placed on Web pages or used for printing. Access files are expected to be of good quality, but they may be modified to meet the needs at hand.

Thumbnail files are very small files for use in databases or Web pages.

Recommendations for preparing digital images for future use and long-term preservation:

Image Type: Printed Text

  • Master
    • Scan Type: Bitonal
    • Resolution: 400-600 DPI
    • Format: Uncompressed TIFF
  • Access
    • Type: 8-bit grayscale/24-bit color
    • Format: JPEG
    • Compression: Medium
    • Spatial Resolution: Resize to 1024 x 768 pixels
  • Thumbnail
    • 4-bit grayscale/8-bit color
    • Format: GIF
    • Spatial Resolution: Resize to 150-200 pixels across the long dimension 72 DPI

Image Type: Damaged Printed Text

  • Master
    • Scan Type: 8-bit grayscale or 24-bit color
    • Resolution: 400 DPI
    • Format: Uncompressed TIFF
  • Access
    • Type: 8-bit grayscale/24-bit color
    • Format: JPEG
    • Compression: Medium
    • Spatial Resolution: Resize to 1024 x 768 pixels
  • Thumbnail
    • 4-bit grayscale/8-bit color
    • Format: GIF
    • Spatial Resolution: Resize to 150-200 pixels across the long dimension 72 DPI

Image Type: Handwritten Manuscripts

  • Master
    • Scan Type: 8-bit grayscale or 24-bit color
    •  Resolution: 400-600 DPI
    • Format: Uncompressed TIFF
  • Access
    • Type: 8-bit grayscale/24-bit color
    • Format: JPEG
    • Compression: Medium
    • Spatial Resolution:Resize to 1024 x 768 pixels
  • Thumbnail
    • 4-bit grayscale/8-bit color
    • Format: GIF (or JPEG)
    • Spatial Resolution: Resize to 150-200 pixels across the long dimension 72 DPI

Image Type: Maps, Drawings

  • Master
    • Scan Type: 8-bit grayscale or 24-bit color
    • Resolution: 200-400 DPI
    • Format: Uncompressed TIFF
  • Access
    • Type: 8-bit grayscale/24-bit color
    • Format: JPEG
    • Compression: Medium
    • Spatial Resolution: Resize to 1200 pixels across the long dimension (large maps) size to 640 x 480 pixels (small maps)
  • Thumbnail
    • 4-bit grayscale/8-bit color
    • Format: GIF (or JPEG)
    • Spatial Resolution: Resize to 150-200 pixels across the long dimension 72 DPI

Image Type: Black & White Photographs

  • Master
    • Scan Type: 8-bit grayscale
    • Resolution: 400-600 DPI
    • Format: Uncompressed TIFF
  • Access
    • Scan Type: 8-bit grayscale
    • Format: JPEG
    • Compression: Medium
    • Spatial Resolution: Resize to 1024 x 768 pixels
  • Thumbnail
    • 4-bit grayscale
    • Format: GIF (or JPEG)
    • Spatial Resolution: Resize to 150 – 200 pixels across the long dimension 72 DPI

Image Type: Color Photographs

  • Master
    • Scan Type: 24-bit color
    • Resolution: 400-600 DPI
    • Format: Uncompressed TIFF
  • Access
    • Type: 24-bit color
    • Format: JPEG
    • Compression: Medium
    • Spatial Resolution: Resize to 1024 x 768 pixels
  • Thumbnail
    • 8-bit color
    • Format: GIF (or JPEG)
    • Spatial Resolution: Resize to 150 – 200 pixels across the long dimension 72 DPI

Image Type: Works of Art on Paper

  • Master
    • Scan Type: 8-bit Grayscale/ 24-bit color
    • Resolution: 400 DPI
    • Format: Uncompressed TIFF
  • Access
    • Type: 8-bit grayscale/24-bit color
    • Format: JPEG
    • Compression: Medium
    • Spatial Resolution: Resize to 1024 x 768 pixels
  • Thumbnail
    • 4-bit grayscale/8-bit color
    • Format: GIF (or JPEG)
    • Spatial Resolution: Resize to 150 – 200 pixels across the long dimension 72 DPI

Image Type: Microfilm

  • Master
    • Scan Type: Bitonal
    • Resolution: 400-600 DPI (blown back to original size)
    • Format: Uncompressed TIFF
  • Access
    • Type: 8-bit grayscale/24-bit color
    • Format: JPEG
    • Compression: Medium
    • Spatial Resolution: Resize to 1024 x 768 pixels
  • Thumbnail
    • 4-bit grayscale/8-bit color
    • Format: GIF
    • Spatial Resolution: Resize to 150-200 pixels across the long dimension 72 DPI