All images are digitized | All jpegs/tiffs display outside Library of Congress | View All
Digitizing the Negatives
JJT, Inc., of Austin, Texas, scanned the original glass plate negatives using an overhead capture MARC II digital camera in May 2001. Each negative was scanned at a resolution of 10,000 pixels on the long side with the short side scaled in proportion. Though the original negatives are black-and-white, the scans were produced using RGB color to facilitate a specialized book publication project. Each color channel was scanned at 12 bits per pixel and archived at 16 bits per pixel with an uncompressed size of approximately 260 megabytes per file. The uncompressed archival images available online were generated from the RGB master images.
The image deterioration visible on some photos occurred when the glass plates were submerged for several days in the 1913 Dayton, Ohio, flood. In order to prevent further damage, the negatives were scanned emulsion "up", with the glass side of the negatives placed directly on the scanning surface. The images were then digitally reversed to be right reading. All of the negatives were scanned "as is." No attempt has been made to digitally clean or replace damaged portions of the image.
Specifications for the Collection
Uncompressed Archival TIFF Images
| Spatial Resolution: | 5,000 pixels on the long side with the short side scaled in proportion for file names ending in u.tif (17-20 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 |
Highest Resolution TIFF Images
| Spatial Resolution: | 10,000 pixels on the long side with the short side scaled in proportion (approximately 260 megabytes) |
| Tonal (pixel depth) resolution: | 16 bits per pixel (RGB) |
| 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 (40-50 kilobytes); 1024 pixels on the long side with the short side scaled in proportion for file names ending v.jpg (90-100 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 |
