Edward S. Curtis's The North American Indian
The scanning and image processing was executed on site in the library in April of 1999 by JJT Inc. using a customized, high-end digital camera, the Kontron MARC II. The camera allowed flexibility in capturing both the large individual portfolio plates (images averaging 12 by 16 inches) and the plates in the bound text volumes (averaging 5 1/2 by 7 1/2 inches). A special book cradle was designed by JJT to hold the bound volumes open under glass at an angle just over 45 degrees, to protect the bindings and minimize image distortion. The actual image capture was made from an image reflected in a mirror held perpendicularly to the book cradle. Image evaluation and processing followed the approach described for digitizing the photographs from the Robert Runyon Collection at the University of Texas
The illustrations were scanned in color at a very rich bit depth, with capture at 12-bit-per-color-per-pixel or 36-bit resolution and output at 8-bit-per-color-per-pixel or 24-bit resolution. The settings enhanced the subtle brown tonalities and soft focus of the Curtis images, which are not sepia photographs but instead photo engravings printed in brown ink on cream colored paper. The images may look quite brown on certain monitors: they were created using the default RGB color space (sRGB). This should be considered in determining profile settings for viewing or printing the files.
The images were not modified after being written to files. All files are archived offline on CD-ROMs. The original scans are stored as uncompressed TIFFs, averaging around fifty megabytes each. See below for specifications for the derivative images. Copies of the images were sent to Library of Congress, where the derivative images are mounted on a server.
Following the advice of Library of Congress staff, several efforts were undertaken to document physical qualities of the original source materials. This includes defining the outline of the captured image as extending to the impression of the engraving plate, leaving a margin around the image. Dimensions of the plate outlines were recorded, as were the image dimensions, which apparently varied according to how Curtis may have modified the negatives. The measurements are indicated in chart form for the images from each text volume (see, for example, Volume 1) and in the catalog records for the individual portfolio plates.
Consecutive numbers assigned by project staff to the volume and portfolio series of plates became the logical identifiers for the images, using naming conventions suggested by the Library of Congress National Digital Library Program. For instance, ct1008r.jpg is the eighth image in the tenth bound text volume, and it is a reference, or screen-sized, digital image. To assist catalogers by providing online access to the images, the Library of Congress mounted the images and registered handles as persistent identifiers in advance of cataloging.
| Resource | Scan setting | Archival scan | Derivative formats: reference and larger |
Derivative format: thumbnail |
|---|---|---|---|---|
| Portfolio images | 350 dpi, color, 24 bit per pixel |
TIFF uncompressed, 5000 pixels on long side |
JPEG, high quality 10-15:1 compression 640 x 480 pixels 1024 pixels on long side |
JPEG 150 pixels on long side |
| Volume images | 400 dpi, color, 24 bit per pixel |
TIFF uncompressed, 3000 pixels on long side |
JPEG, high quality 10-15:1 compression 640 x 480 pixels 1024 pixels on long side |
JPEG 150 pixels on long side |