Technical Information

• Scanning and Compression Specs
• CONTENTdm Software

Scanning and Compression Specs

Conservation Imaging Systems, Inc. of Seattle, Washington scanned the original prints, postcards, transparencies, film negatives, glass negatives, and glass lantern slides on an Epson 1640 flatbed scanner and a Scitex SmartScan. Oversize images (those larger than 11 x 17 inches), and anything else that could potentially harm the glass surface of the flatbed scanner, were captured with a Phase One FX digital camera. Some negatives were scanned on a Flextight 848 flatbed scanner. Color images were scanned as 24-bit RGB color, and black-and-white images are scanned as 8-bit grayscale, except when 24-bit RGB color was used to capture tone color of black-and-white images.

Images were scanned as uncompressed PC TIFFs (Tagged Image File Format) at a spatial resolution of approximately 3000 pixels on the long side. Scanning to this size allowed for the creation of 8x10 prints directly from the TIFFs.

TIFF images were not retouched, enhanced, or edited. They were delivered to each partner organization on CDs, and serve as the master digital images for the owning institution, but are not included online.

Any exceptions to the above information will be noted in the metadata record of the appropriate image.

The TIFFs were converted to compressed JPEG (Joint Photographic Experts Group) files via a batch process using Adobe PhotoShop version 6.0.

The process began by resizing the TIFFs. Images that were longer in the horizontal dimension reduced to 640 pixels (spatial resolution) in that dimension, allowing the vertical to adjust proportionally; images that were longer in the vertical dimension reduced to 600 pixels (spatial resolution), allowing the horizontal dimension to adjust proportionally. These sizes allow for maximum viewing on standard-size computer monitors.

The images were then saved using JPEG compression in progressive format set at three scans, and compression level 3 (out of a possible 12). This compression level allows for an image that looks good on screen but will not be adequate for printing.

The final part of the process used the Unsharp Mask on all images, with the amount set at 150%, the radius 1.0 pixels, and the threshold at 0 level.

The "Property Of..." statement, or band, was added to the JPEGs by batch process using the CONTENTdm Software Suite, which was also used for metadata capture.

Partner organizations may have enhanced or edited their JPEG images on a case-by-case basis. We asked that they document the extent of those edits in the "Digital Reproduction Information" field associated with the image.

^ top ^  

CONTENTdm Software

The collections on this site all utilize the CONTENTdm Software Suite, a product of DiMeMa, Inc. CONTENTdm provides tools for digital collection management. It is scalable and is optimized for exceptionally large datasets. It permits the creation of multiple collections within one system and allows searching both individual collections or across multiple collections.

For more information about CONTENTdm, visit http://contentdm.com.

^ top ^