Architecture and Interior Design


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Building the Digital Collection

In order to offer extensive reference service to the nation, the Library of Congress will provide online access to over 500,000 items from its pictorial collections during the next few years. The reproductions will have sufficient quality to meet general reference needs, and, in a few instances, museum-quality facsimiles will also be created.

The images in the Gottscho-Schleisner collection grew out of a special project to make preservation copies of deteriorating nitrate and diacetate negatives in Library of Congress photographic collections. (Some color transparencies were also copied at this time.) The original negatives were copied onto larger cut film in the late 1980s. At the same time, in order to produce a reference service videodisc, the Library produced an additional 35mm film copy of the negatives. The contractor, Stokes Imaging of Austin, Texas, produced the analog videodisc from the 35mm film in a two-step process. First, Stokes created a set of interim digital images with the moderate spatial resolution of 560x420-pixels. This set of digital images was archived. Second, the digital images were processed to create the analog video frames.

The current set of larger images (the images requested by the action of clicking the thumbnail) are reprocessed versions of the archived 560x420 digital images. The black-and-white images have a tonal resolution of 8 bits-per-pixel (256 shades of gray), while the color images have a tonal resolution of 24 bits-per-pixel (16 million shades). All have been compressed with the JPEG (Joint Photographic Experts Group) algorithm. Uncompressed versions of the images at the same resolution are held by the Library.

The "inline" thumbnail images for the Gottscho-Schleisner collection are in the GIF (Graphics Interchange Format) format and have a spatial resolution on the order of 150x150 pixels. Both the black-and-white and color images have a tonal resolution of 8 bits-per-pixel. These are the images displayed with the bibliographic records.