Frank M. Hohenberger Photograph Collection

Technical Implementation

Online Web Accessible Search and Discovery

The online web accessible search and discovery functions have been built on the Fedora Digital Repository system. The MODS records are indexed for searching. The interface is a Java Struts application, which uses CQL queries to access the Fedora repository. The images are linked via PURLS.

Digitization Process

All digital files included in the Hohenberger collection must adhere to stringent guidelines. Color balancing, when necessary, is done prior to scanning using the Silverfast software product as the driver for Epson 10000XL flatbed scanners. All scanners and monitors are color calibrated regularly to ensure accuracy and consistency of the digital images.

The digital files are created by scanning Hohenberger's transparencies. The small transparencies, 2"x2" or smaller, are scanned at 1200 dpi. All other transparencies are digitized at 800 dpi. Color images are scanned at 24-bit color with imbedded Adobe1998RGB color profiles. Black and while images are digitized at 8-bit grayscale with the imbedded profile of Gray Gamma 2.2. The inclusion of the profiles helps ensure that the image will reproduce as accurately as possible. All master files are scanned at 100% of the original size and saved as uncompressed TIFF files.

Quality Control

All Hohenberger master files must pass a two-step quality assurance procedure. The first step is an automatic quality control process that ensures valid and well formed files. A set of computer programs systematically examine the embedded TIFF tag of every digital file to verify that all files are named according to convention, that they are uncompressed TIFF files, that each file has an embedded profile appropriate to its bit depth, and that all images were scanned at the appropriate resolution.

Once the files pass the automatic quality control, a portion of the files are manually examined to ensure good visual quality. Each file selected is examined at 100% pixel display to see that the image orientation is correct, that the color balance matches the original item as closely as possible, that the scan is sharp and in-focus, and that no digital artifacts of scanning are visually present. To aid in the manual quality control process, the physical images are examined simultaneously to compare color fidelity. If any inconsistencies are found in either the automatic or manual quality assurance checks, the item in question is rescanned until it is acceptable.

Web Derivatives

After an image passes both automatic and manual quality control, derivatives are created for web display. We create three web deliverable files - a thumbnail, a small screen size and a full screen image. The thumbnail is 200 pixels on its longest dimension. The small screen image is to be 600 pixels on its longest dimension and the full screen is scaled to be 1000 pixels on its longest dimension. The derivative files are saved as jpeg files. The master files are sent to long-term tape storage.