Technical Information

CSC of Chantilly, Virginia, scanned the original glass plate negatives using an overhead capture Sinar 54 digital camera beginning in 2008. Each negative was scanned at a resolution of 10,000 pixels on the long side with the short side scaled in proportion.

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 153 megabytes)

Tonal (pixel depth) resolution:

16 bits per pixel (grayscale) Note: Some older versions of image viewers and editing software cannot handle 16 bit images.

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 (20-100 kilobytes); 1024 pixels on the long side with the short side scaled in proportion for file names ending v.jpg (80-210 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 10 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