Generally speaking, the Library reproduces pictorial items as a set of three digital images:
(1) an uncompressed archival image,
(2) a compressed reference image, and
(3) a thumbnail image.
With this collection, the Library is providing access to the
uncompressed archival image as well as to the compressed reference image. By doing so, the Library hopes to serve patrons who would like a file free of the artifacts that result from the JPEG compression algorithm. In this case, since the archival and reference files have the same 1,200-pixel spatial resolution (see
The digital images in the "Votes for Women" reference aid were produced by scanning a few vintage prints and many 8x10-inch copy negatives selected from the Prints and Photographs Division's extensive copy photograph file. (See: By Popular Demand). All but two sets of the digital images were produced by JJT, Incorporated, of Austin, Texas, which scanned the copy negatives with a Kontron digital camera. Library of Congress staff scanned the vintage prints on a Horizon flatbed scanner.
Uncompressed Archival Images
Tonal (pixel-depth resolution): Color: 24 bits-per-pixel; black and white: 8 bits-per-pixel
No sharpening
Uncompressed
Tagged Image File Format (TIFF)
NOTE 1: The resolution of 1,200-pixels was selected for the digital images in this collection as consistent with the resolution planned for digital images of other copy negatives and copy transparencies. Some subsequent Library of Congress pictorial collections--especially when original materials rather than copy photographs are being digitized-- will offer archival images at resolutions of 3,000 and 5,000 pixels.
Tonal (pixel-depth resolution): Color: 24 bits-per-pixel; black and white: 8 bits-per-pixel
Sharpened
JPEG compression to yield average compression of 10:1 for grayscale and 15:1 for color
JFIF format/headers
Tonal (pixel-depth resolution): 8 bits-per-pixel
Palettes optimized (adaptive palettes) for each image
Sharpened
Uncompressed
Archived copy: Tagged Image File Format (TIFF)
Online copy: GIF format, produced by the Library of Congress. These are the images displayed with the bibliographic records.