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Collection Architecture, Design & Engineering Drawings

Technical Information

Scans of Bain Collection glass negatives (the bulk of what is presented online) and photographic prints (selectively represented online) have somewhat different qualities.

Glass Negatives

During 2004-2006, JJT, Inc., of Austin, Texas, and Datatrac Information Services of Chantilly, Virginia, scanned the negatives. Both used an overhead Sinar 54 digital camera to scan the 39,744 glass negatives (measuring in sizes ranging between 2-1/4 x 2-1/4 " and 8 x 10 inches). The images were captured in grayscale at a spatial resolution of approximately 5,000 pixels on the long side and a tonal resolution of 8 bits per pixel. The negatives were scanned with the emulsion side up to protect the fragile surface. The negatives display online as they would have been printed. Words sometimes appear in mirror image because they were notes written on the emulsion side for identification purposes, not necessarily to be printed with the image--the words were often cropped out.

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 master and derivative files are available online. Digital images of each negative display in each bibliographic record. Records for negatives can be recognized by information that appears next to the Digital ID, which says, "digital file from original neg." The specifications for the master and derivative files are as follows:

Uncompressed Archival (Master) 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

Compressed Service Images

Spatial resolution:
640 pixels on the long side with the short side scaled in proportion for file names ending r.jpg (25-190 kilobytes); 1024 pixels on the long side with the short side scaled in proportion for file names ending v.jpg (80-460 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

Photographic Prints

Most digital images for photographic prints were scanned from copy negatives. (These can be recognized by the information next to the Digital ID, which says "b&w film copy neg.") Scans from copy negatives were generally digitized at a relatively lower resolution, approximately 1,500 pixels on the long side for the uncompressed archival image. Some scans produced more recently are as large as 4,000 pixels on the long side.

In a few cases, the original photographic print was scanned. (These can recognized by the information next to the Digital ID, which says, "digital file from original photo.") In such cases, the size is between 3,000 and 5,000 pixels on the long side for the uncompressed archival image.

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