Digital Gateway
Washington University Digital Gateway

Digital Imaging Standards

Hardware & Software

Scholarly Publishing has the following scanners available for internal library use. Please contact Digital Library Services if you would like to use one of these scanners

The Atiz scanners use BookDrive capture software to scan images and editor software to process images from RAW to TIFF files.

The Table Top Scribe uploads images directly to Internet Archive (IA) for processing and quality control. The images are republished in Washington University’s IA collection.

The Epson scanners use Epson capture software for scanning images.

Scholarly Publishing uses Adobe Creative Suite to process and edit images.

Adobe Bridge is recommended for managing images and tracking progress.

Camera Raw is recommended for cropping and converting RAW image files to TIFF.


Image Capture Requirements

  • Capture documents from outside front cover to outside back cover and spine, if possible
  • Images should be kept in original order and files should be named in original, serial order
  • Page images should be captured at one single page per file and two page spreads should be captured as two files
  • Page images should be rotated (if applicable) so images are in proper reading order when opened
  • Folded documents should be unfolded before imaging
  • Oversized documents should be captured with copy stand and digital camera
  • Include a documents' unfolded size when considering image capture method
  • A book cradle should be used to support fragile materials
  • If documents fit easily onto standard flatbed scanner and will not be damaged by being flattened, it is acceptable to use a flatbed scanner
  • If volumes have missing pages, indicate which pages in the appropriate metadata field

Pixel Dimensions

  • Pixel dimensions of the digitized image are dependent upon the size of the original, the ppi (dpi) at which it is scanned, or the resolution of the camera
  • For most files, at a minimum, images should be captured at 4,000 pixels along the longest side
  • When capturing images with a camera documents should fill the viewfinder as much as possible to maximize resolution, and on a flatbed scanner, the ppi (dpi) should be increased to the desired level

Resolution

  • Images should be captured at 600ppi at original size
  • Resolution should be achieved without interpolation, if possible

Color


Color Space

  • RGB is the recommended color space for archival master copies
  • Cameras should be white balanced by shooting a white balance reference card in the same light as the document
  • Standardized color reference points should be captured with each document in the event the images need to be color corrected
  • For grayscale: use a Photographic Gray Scale (such as Kodak Gray Scale) to ensure gray values fall within recommended aimpoints. Color bars with white, midpoint, and black aimpoints may also be used.
  • For color: compare with color bars (such as Cameratrax) to ensure accurate color reprensentation
  • When measuring aimpoints, measure image area of at least 5x5 pixels
  • See NARA's Technical Guidelines for Digitizing Archival Materials for Electronic Access

Image Color Requirements & Bit Depth

Color

  • Color imaging should be used when color is an important attribute of the document
  • Color imaging should be used in the majority of cases
  • Images should be captured at a minimum of 24-bit-color
  • If possible, to preserve the highest level of detail, 48-bit-color should be used for archival purposes.

Grayscale

  • If color content does not exist or is not deemed significant, the material may be captured in grayscale
  • Images should be captured using 8-bit grayscale
  • If the imaging operator is unsure whether to capture the image in color or grayscale, it is safe to assume that color image capture should be used

Bitmap

  • Bitmap is rarely desirable
  • Please note that some batch processes may be inhibited when using bitmapped images (for example: batch processing tiffs to jpegs using Photoshop)

File Formats

Master Files

  • Files should be saved in an uncompressed, lossless format
  • TIFF is the preferred file format

Access Images

  • Access images may be compressed format, such as JPEG and migrated to a lower resolution for web delivery

File Names

  • Image files should follow file naming convention set for each set of materials
  • File names should be constructed so files can be easily located
  • File names should facilitate management of variant forms of an image (master file, access file, thumbnail file, etc.)
  • File names should never contain spaces and should not limit interoperability, such as using system specific syntax or characters. The only special characters used should be underscores, hyphens, or periods
  • Scholarly Publishing recommends: identifying project code, date of publication, and serial order number in filenames to ensure each filename is unique

Quality Control

  • At minimum, 10% of each batch of digital images should be inspected for compliance with above specifications
  • All images should be in focus
  • Digital image should be accurate representation of the original, including clearly legible text and sharp illustrations

Metadata

A discussion of metadata management is needed before beginning any digital imaging project, the depth of which is outside the scope of this resource. Please consult with Scholarly Publishing if you have questions about managing your project data.


Minimal recommendations

Be consistent! Agree on authority files (LOC, ULAN, AAT, etc.) or local terms and ensure they are used Ideally metadata should be encoded in XML using DC, VRA, CDWA or another accepted standard. If XML is not an option, Excel spreadsheets should be used


Delivery & Preservation

Scholarly Publishing recommends making image collections available online via ARTstor's Shared Shelf, Omeka, Internet Archive. Scholarly Publishing can assist you in developing online collections

For preservation, Scholarly Publishing recommends storing images on a secure file server and ingesting image metadata in Fedora


Sources
Getty Introduction to Imaging - Image Capture
University of Michigan Digital Library Production Services Digital Conversion Unit
LOC - Image Quality Standards by Document Type and Expected Outcome
NARA - Technical Guidelines for Digitizing Archival Materials for Electronic Access

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