Why you should preserve documents on 35mm microfilm instead of 16mm microfilm
There are several options for choosing the type of microfilm and layout to use when preserving digital documents.
The three options for microfilm are the following:
- 16mm archival microfilm 100’ length
- 16mm archival microfilm Thin Based 215’ length
- 35mm archival microfilm 100’ length
16mm microfilm is best used in a simplex format for documents up to 15” tall and filmed at a reduction ration of 24x. Duplex formats are not recommended for document preservation because the reduction ration would have to be 40x or more. Reduction ratios higher than 32x are generally not recommended since the resolution of the documents will be lower when viewing, scanning or printing back at full size. The cost per document for 16mm microfilm 100’ in length is higher than 16mm microfilm 215’ in length. Both cost more per document than 35mm.
35mm microfilm is the most flexible option and potentially least expensive price per document.
Flexibility comes from being able to record virtually all standard document sizes from 8.5” x 11” up to 36” x 48” or longer. This allows documents of all sizes to be interfiled on the microfilm. This is not possible on 16mm microfilm.
The documents can be laid out in one of several formats: simplex, compact density and maximum density. Simplex is generally not recommended because it is more costly than the other formats with no benefit. The compact and maximum density formats are good choices, but the maximum density is preferred in order to achieve the lowest cost per document.
35mm Microfilm laid out for maximum density produces the highest number of documents per roll of film, and it has the flexibility of interfiling all document sizes. A recent survey of Ohio county and state government agencies found 57 percent placed a high value on systems that would allow interfiling of all document sizes.
A high document count on a roll of microfilm will lower the cost per document to produce the film and store the film for long-term preservation.
35mm microfilm with maximum density should be the microfilm type and layout for document preservation.