Digitizing the Collection |
During 2002-2003, JJT, Inc., of Austin, Texas, scanned the Brady-Handy Collection. They used an overhead MARC II digital camera to scan the 4993 glass negatives (measuring in sizes ranging between 2-1/4 x 3-1/2" and 8 x 10 inches). The images were captured in grayscale at a spatial resolution of approximately 10,000 pixels on the long side and a tonal resolution of 16 bits per pixel.
With today's resources, these very high-resolution images require significantly increased costs, particularly in time spent capturing, inspecting, and loading the files. For most collections in the Prints and Photographs Division, online digital images, even at lower resolutions, play an important preservation role as surrogates that reduce handling of the original pictures. The high-quality derivative files are available online, but the master files have been archived. Digital images of each negative display in each bibliographic record.
Specifications for the Collection
Uncompressed Archival Images
| Spatial Resolution: | 5,000 pixels on the long side with the short side scaled in proportion for file names ending in u.tif (17-23 megabytes) |
| Tonal (pixel depth) resolution: | 8 bits per pixel (grayscale) |
| Image enhancement: | None. |
| File format: | Tagged Image File Format (TIFF) ver. 6.0 |
| Compression: | None |
Compressed Service Images
| Spatial resolution: | 640 pixels on the long side with the short side scaled in proportion for file names ending r.jpg (22-140 kilobytes); 1024 pixels on the long side with the short side scaled in proportion for file names ending v.jpg (42-290 kilobytes) |
| Tonal (pixel depth) resolution: | 8 bits per pixel (grayscale) |
| Image enhancement: | Mild sharpening |
| File format: | JPEG |
| Compression: | Compressed to yield an average compression ratio of 10:1 |
Thumbnail Images
| Spatial Resolution: | 150 pixels on the long side with the short side scaled in proportion for file names ending in t.gif (approximately 20 kilobytes) |
| Tonal (pixel depth) resolution: | 8 bits per pixel (grayscale) |
| Image enhancement: | Mild sharpening |
| File format: | Archived copy: TIFF - Tagged Image File Format Online copy: GIF - Graphics Interchange Format |
| Compression: | Archived copy: Uncompressed Online copy: Compression native to the GIF format |
Master Archived Images
| Spatial Resolution: | 10,000 pixels on the long side with the short side scaled in proportion (approximately 100 megabytes) |
| Tonal (pixel depth) resolution: | 16 bits per pixel (grayscale) |
| Image enhancement: | None |
| File format: | Tagged Image File Format (TIFF) ver. 6.0 |
| Compression: | None |
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Library
of Congress(August 6, 2004 )