The quality of the microfilm from which one scans can make a big difference in the ability of your readers to search the final digital product. Many things influence the quality of the digitized copy and, particularly, the ability of an optical character recognition (OCR) program to make keyword searching effective.
Some standard references regarding microfilm quality and selection for digitization include:
Kelly Barrall and Kristine Guenther, Microfilm Selection for Digitization. OCLC Online Computer Library Center, 2005. http://www.loc.gov/ndnp/guidelines/NEH_MicrofilmSelectionNDNP.pdf.
RLG Guidelines for Microfilming to Support Digitization http://www.oclc.org/content/dam/research/activities/presmicrofilm/microsuppl.pdf
NDNP Technical Specifications for 2015 Awards, [Microfilm] Selection, pp. 5-6.http://www.loc.gov/ndnp/guidelines/NDNP_201517TechNotes.pdf
Lisa Fox, ed. Preservation Microfilming: A Guide for Librarians and Archivists. 2nd Edition. ALA, 1996. http://saa.archivists.org/store/preservation-microfilming-a-guide-for-librarians-and-archivists-2nd-ed/175/
Summary of Microfilm Readings that Meet National Standards for Digitization
- Visual inspection with a 10x scale lupe shows crisp text
- Reduction ration less than 20x
- Resolution of 5.0 or higher
- Density on a reel of film runs between 0.90 and 1.20
- Difference in density readings between exposures and within an image is no higher than 0.20.
Microfilm Standards and Quality Preliminaries
- Use the second generation of the film, if possible. The first generation master is the film that comes right out of the camera and may be irreplaceable. The second generation, often called the print negative, is the one ideally used to make duplicate film or from which to scan. The third generation, named the service copy, is a positive and is the copy that readers used in your reading room. It is not, generally speaking, suitable for scanning as positive film has more “noise” than negative film and this “noise” will weaken the OCR process outcome. In addition, service copies are usually scratched by use in a microfilm reader and those scratches will also impact the quality of a scan.
2. Look at the service copy to see if you can expect the negative to be marred by any of the following problems.
Lights out of place when filming, leading to glare obscuring text.
Camera not perfectly parallel to the page can lead to a trapezoidal shape and skew, affecting OCR quality and the reliability of keyword searching.
3. Use the visual inspection of your service copies, keeping in mind all of the above, and make a judgment about how many pages out of the whole reel are legible.
To do a more sophisticated analysis of your film suitability, use the reference books on microfilm standards listed above to measure:
- Reduction Ratio
Remember! Scanning vendors can make good digital Images out of less than perfect film but start with the best film you can locate!
Return to Digitizing the Newspapers of Connecticut.