Does it matter whether I record my documents on 16mm or 35mm microfilm?
A previous blog post explained the importance of microfilm for long term preservation of documents as an addition to digital storage. Second to recognizing the importance of archiving critical documents on microfilm is choosing the correct microfilm for your application For example, many times organizations settle for archiving documents larger than 12” x 18”, such as engineering or technical documents, on to 16mm microfilm. This can be a big mistake in terms of resolution obtained and future readability both by scanner or human eye.
There are three major types of microfilm media used for long term preservation: 16mm roll microfilm, 35mm roll microfilm and 35mm microfilm mounted in aperture cards. The type of media utilized for preservation microfilming should be matched to the type of document being recorded in order to obtain optimum resolution for future viewing and printing.If the image does not have sufficient resolution for a human or a scanner to read the data, the microfilm fails as a “reference archive” for the purpose of preserving the document. Generally this means a minimum resolution of at least 300 dpi is necessary. Resolution below 230dpi should be avoided.
A Guide to Choosing the Correct Microfilm
When to Use 16mm Microfilm
If all documents being archived are office documents (letter, legal, and ledger size – up to 12″ x 18″ landscape orientation or A3 size landscape orientation), the use of 16mm roll microfilm as a reference archive media will, in most cases, provide the desired result. Most archive recording devices in use are capable of producing archived images at resolutions of 285 dpi or greater on 16mm microfilm.
(Screen shot to the right shows documents 11″ x 17″ and smaller composed on 16mm microfilm using Tameran Microfilm Roll Composer.)
When to Record on to 35mm Microfilm
If the materials being recorded include larger documents such as engineering drawings, plat maps or ledger books (portrait orientation), the use of 35mm archive media in the form of roll film or mounted aperture cards is required to produce images that have sufficient resolution. Only a few archive recording devices in use have the capability to produce archive images with resolutions of 230 dpi or greater on 35mm microfilm.
(Screen shot to the right shows various documents including C (17″ x 22″) and D (24″ x 36″) size on 35mm microfilm created with Tameran Microfilm Roll Composer.)
When to Use Aperture Cards
If your archive system is a continuation of a legacy system that was based upon the use of 35mm aperture cards to store and distribute documents, you may want to continue this system for compatibility. This would be particularly true if you currently have a large legacy collection of aperture cards or if your application requires a unit file for document reference or distribution. Historically, 35mm aperture cards have been used when originals include larger documents such as engineering drawings, plot maps, etc.
Be a Smart Microfilm Consumer
Document resolution is not only affected by archive media width but also by resolution capabilities of the recording device. Be aware when purchasing equipment or services for recording onto 35mm microfilm that not all recording devices have the ability to produce document resolutions of 300 dpi or higher. Ask your service provider what type of equipment they are using and what resolution to expect from their processes.
Recording business critical documents on microfilm is of great importance for preserving documents long term. Not all documents may have a life cycle that necessitates recording onto microfilm, but if you deal with documents that are significant to the creation, maintenance or legal implication of a manufactured product with a long “shelf life”, government records, land records, etc. then recording on the correct microform should not be overlooked so documents retain their original integrity and resolution.