The Samuel F. B. Morse Papers were microfilmed by the Library of Congress Photoduplication Service in 1975. All thirty-five reels of this microfilm were digitized, producing approximately 50,000 images. Digitization of the microfilm was performed offsite by Preservation Resources of Bethlehem, Pennsylvania, under contract to the National Digital Library Program.
The Morse Papers were scanned as 200 dpi, 8-bit grayscale images that were compressed using JPEG compression, producing images in the JPEG File Interchange Format (JFIF). This format is typically used to digitize historical manuscripts because of its ability to capture and display the diversity of tones in manuscripts and the varying nuances produced by handwriting, pencil, and ink. Capturing images in grayscale can often also suppress the bleedthrough typical of handwritten documents in the Morse Papers. (Bleedthrough means that the ink or printing on the verso, or back, of a page can be seen on the recto, or front.) Because JPEG images require considerable time to download, grayscale GIF images were created for convenient access when using the NDLP page-turner feature. GIFs were generated from grayscale TIFF images by Preservation Resources.
Twenty-two original letters from the Addition series were digitized as 300 dpi grayscale images with a Phase I camera by the ITS Digital Scan Center at the Library of Congress.
The quality of the microfilm of a manuscript collection can affect the resulting digital images. The Morse Papers microfilm was scanned from a duplicate negative microfilm, which was copied directly from the archival microfilm and produced for scanning by Preservation Resources. The negative can reduce the appearance of flaws such as dust in digital images. Preservation Resources took pains during the duplication process to compensate for the high density range of the master microfilm.
Other image-quality issues arise from the condition of the original manuscripts and the way the collection was microfilmed. A wide range of tonal values, document sizes, and document orientations appears on the Morse Papers microfilm. The physical state of the original manuscripts varies from good to poor, and the microfilm images reflect this. Many of the original materials are discolored, stained, or fragile. Their digital images may therefore show discolorations, heavy fold markings, and various tones in the paper. Items may sometimes show bleedthrough that even the grayscale format could not suppress. Also, some digital images of documents appear to have light or faded text that may be difficult to read. This is often either because the handwriting strokes are very thin or because the ink or pencil has faded on the original materials. In addition, some correspondence shows what is known as writing-over, or text over text: to save paper, the writer has turned a completed page sideways and written new text over and at right angles to the text already on the page. Letterbook images may be especially difficult to read for a different reason. Letterbooks contain letterpress letters, or copies of letters which have been pressed onto tissue-thin paper. The resulting copy can have bleeding handwriting, very faded text, wrinkles, ripped and frayed edges, and other conditions that affect legibility. Some pages are completely illegible. Finally, the Morse Papers consist chiefly of correspondence, the bulk of which has been mounted onto pages of bound volumes. The manuscript leaves were affixed to the pages with a special tape that occasionally obscures text on the edges.