Technical Information

Scanning

The items in this collection were digitized to showcase the rotogravure printing process. High quality images were created working from original print materials.  To minimize risk to the brittle pages, all scanning was done using overhead type scanners.

Uncompressed TIFF images were captured at 300 pixels per inch relative to the original material.  Many of the pages were originally printed using colored ink in a monochromatic way, to create a sepia tone effect. To preserve this design information, those pages were scanned in full color.  Pages originally printed using only black ink were captured in grayscale.

Image Processing

While the TIFFs scanned from the original paper were initially processed for the 1990’s American Memory presentation, additional metadata was added to follow the National Digital Newspaper Program (NDNP) standard in 2015. See http://loc.gov/ndnp for more information about the National Digital Newspaper Program.

Image Specifications

Master image(Not Available via the Website) 
Image resolution: 300 dpi 
Tonal resolution:  24 bit (color) and 8 bit (grayscale) 
File format: TIFF 
Compression: uncompressed

JPEG2000 Service Images 
Image resolution:  300 dpi 
Tonal resolution:  24 bit (color) and 8 bit (grayscale) 
JPEG2000 Compression: 8:1

PDF Service Images 
Image/Tonal resolution: Grayscale, downsampled to 150dpi and encoded using JPEG, medium (or 40) quality setting.

Text Processing

To permit text searching, the images were processed with optical-character-recognition software. Settings allowed automatic zoning to recognize columns and ignore elements containing no text.  Output was in the form of the ALTO XML format, which included the text gleaned from the images, along with information about each character's location and confidence level. One file was created for each page image. More on the ALTO standard can be found at http://www.loc.gov/standards/alto