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 World's Transportation Commission (WTC) collection trace their history to the Library of Congress Optical Disk Pilot Project (ODPP). The original negatives and prints were captured in 1982 and the resulting imagebase was cost-effectively recycled in the 1990s. The image's moderate spatial resolution (560x420-pixels) and certain shortcomings in quality result from the specifics of that initial capture described in more detail below. Please note that other Library of Congress digital reference-access images are at higher resolutions. For example, the images for the Civil War collection on the World Wide Web have spatial resolutions on the order of 1024x768.
The "inline" thumbnail images for the WTC 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. The larger images in the WTC collection have a spatial resolution of 560x420-pixels and are compressed with the JPEG (Joint Photographic Experts Group) algorithm. 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 colors).
The WTC photographs were originally captured for the Optical Disk Pilot Project (1982-1987), an early Library of Congress effort in the development of electronic collections. For the ODPP, the original photographs were copied onto 35mm color motion picture film (in "academy" or "half frame" format) and then tranferred to video on a standard analog film-to-video transfer device. In 1991, when the American Memory project produced a new version of the videodisc, analog video frames were again created from the film. On this occasion, a contractor created intermediate digital images at a resolution of 560x420-pixels by scanning the film. The contractor then used an automated system to write these images to analog video. The current set of images have been reprocessed from this last set of digital intermediates.