Choice of Scanning Approach

The library contracted with JJT, Incorporated, of Austin, Texas to scan all materials that could not be imaged by library staff on a flatbed scanner. The following items were imaged by JJT, Inc.: 107 Civil War sketches by various artists; 50 drawings from a sketchbook depicting the Draft Riots of 1863; 55 sketches, manuscripts and photographs from an album entitled the Point Lookout Sketches; 735 stereographs; 112 images from the War of the Rebellion photograph album; and 274 posters. All items imaged by JJT, Inc. were imaged using a digital camera.

As a separate phase of the project, staff used an Epson Expression 836XL flatbed scanner to image 62 manuscripts and 4 photographs from the William Oland Bourne Papers, 4 pages of the Prison Times, 14 pages of Walt Whitman manuscript letters, 119 pages of manuscript letters by Sarah Blunt, 490 illustrated Civil War Envelopes, and 31 Confederate War Etchings.

Handling

All imaging took place on-site at the New-York Historical Society, under the direction of New York University grant-funded staff. Project staff consulted with the New-York Historical Society Library's Conservator on proper methods of handling before each different format was scanned.

Because of the variety of physical formats, JJT, Inc. devised various methods for handling the materials. For example, a vacuum board, containing small holes distributed evenly throughout the board, held larger posters in place while they were imaged. The board was positioned horizontally for the placement of the poster. A vacuum pump then created an even suction pull throughout the surface of the board, which was then rotated to the vertical position for imaging. The smaller posters and flat items were placed on a horizontal platen. Bound volumes were positioned in a book cradle to protect the spine during imaging.

Specifications for Archival and Derivative Images

For all items, five image files were created: an uncompressed archival file (master file); a small service file derivative; a large service file derivative; a thumbnail image file derivative; and a compressed archival file (reference file). Archival files are 4,000 pixels along the longest edge, and were color corrected, but not sharpened. The service file derivatives and thumbnail derivatives were sharpened. Except for the thumbnail files which are uncompressed, all derivatives were compressed at 90% image quality. Compressed small service images are approximately 500 pixels along the longest edge; compressed large service images are 1,000 pixels along the longest edge; and thumbnails are approximately 190 pixels along the longest edge. The compressed archival images are 4,000 pixels along the longest edge, but were also compressed at 90% image quality.

Procedures Used by Contractor

Archival image files were created first; all other files were derived from the archival image files. JJT Inc. produced archival image files that include a grayscale target. The derivative files were cropped without the target, sharpened, sized, and color corrected. Archival image files produced by project staff during the flatbed scanning portion of the project do not include a grayscale target, as the insertion of the target increases the file size greatly, thereby making a lower dpi necessary to maintain targeted file sizes. The computer monitor that was used to correct images was calibrated using the NARA grayscale. Initial test scans of batch samples were made with a Kodak grayscale. The light in the imaging room was determined to be 170 lux or 17 foot candles. The archival image files were saved in the TIFF format and all derivatives were saved in the JPEG format. Image files were copied to CDs and to Exabyte Magnetic Tape.

All materials imaged by JJT, Inc. were imaged at approximately 400-dpi resolution, with the exception of the larger format posters, which were imaged at approximately 300-dpi resolution. Photographs captured by JJT, Inc. were first imaged at 48 bits-per-pixel color and compressed to 24 bits-per-pixel images except in the case of the large service file derivatives, which were created as black and white 16 bits-per-pixel images, and then compressed to 8 bits-per-pixel images.

Correction and imaging processing executed by JJT, Inc. were performed directly after capture. Correction and final evaluation were performed by a JJT, Inc. staff member with the assistance and oversight of the New York University project manager working on-site at the New-York Historical Society.

Procedures Used for Materials Scanned In-house

For materials scanned by project staff, archival (master) files were produced first, followed by derivatives, which were produced from these archival files. Because of a shortage of hard drive storage, about 10 archival images (TIFF files about 32MB each) were handled at one time as a batch. After color correction, archival files were saved directly to CD-ROM. Derivatives were created in batches from the archival files using Debabilizer software. Thumbnail, large and small service file derivatives were sharpened individually in Adobe Photoshop. Size of images and of image files produced are consistent with those created by JJT, Inc. and meet the standards set by the Library of Congress.

The Confederate War Etchings were scanned at 400 dpi and 36 bits-per-pixel color. Manuscripts and photographs from the William Oland Bourne Papers were arranged by size physically and in the database before imaging; manuscripts from this collection were scanned at different dpi according to size, ranging from 600 dpi to 700 dpi and 24 bits-per-pixel color. The Walt Whitman letters and the Sarah Blunt letters were scanned at 700 dpi and 24 bits-per-pixel color. The Civil War Envelopes were scanned at 725 to 775 dpi depending on size and 36 bits-per-pixel color. Photographs of the Bourne Papers were first captured at various dpi levels and 36 bits-per-pixel color. The largest photograph was scanned at 400 dpi and 36 bits-per-pixel color and the small photographs were scanned at 1,200 dpi and 36 bits-per-pixel color. The large service copies of all photographs were made to grayscale (256 grays) using the Debabilizer software program. All items originally scanned at 36 bits-per-pixel color were scaled down to an 8 bit color channel in Adobe Photoshop. As a final outcome, all images are 24 bits-per-pixel color or 8 bits-per-pixel black and white as in the case of the large service files of the photographs.