Why then, should a user consider adopting microfilm for an application? Let's review some of the reasons records managers chose microfilm in the past. There are still, in fact, many veteran microfilm clients who see no compelling reason to switch to newer and more expensive technologies, when microfilm continues to serve their requirements.

Let's look at media costs. Despite falling prices for both magnetic and optical media, microfilm remains the least costly form of document storage. The packing density of microfilm far exceeds that of digital media. When comparing packing densities, we generally express microfilm storage in terms of pages per a 4"x4"x1" roll of 16mm film, while we measure digital disk capacity in terms of bytes, kilobytes, megabytes and gigabytes. Discussing billions of bytes seems less impressive if we consider that, even after compression, the average letter-size page requires approximately 50,000 bytes of disk space.

The archival nature and legal acceptability of microfilm is undisputed. Digital data and images, while regularly accepted on a de facto basis under the "best-evidence" rule, lack the regulatory certification or de jure standing of microfilm. Projected estimates by various manufacturers regarding the archival life for optical disk media vary widely. The estimates are generally based on the life of the base medium, rather than the information contained. The wide variation among the estimates has led wags to facetiously suggest that "the archival life of an optical disk is probably somewhere between five years and one hundred years, whichever comes first!"

Legal and archival considerations aside, it is important to consider the more practical aspects of a digital disk's continued useful life, periodic system upgrading may require changes to, or even from, an existing digital imaging system. Despite an ongoing effort for industry standardisation, most digital imaging software systems remain proprietary. When changing to a completely new vendor's system, it might even require retaining a suitable disk drive and software to allow access to archived information stored on older disks.

There are other considerations. As newer and more advanced digital systems evolve, converting information from an older system to a new one presents a formidable challenge and usually requires expensive conversion software to be written. This problem could be avoided if the original paper documents were properly microfilmed first, and the film scanned for input to a digital system. Going to a new digital system in the future would simply mean scanning the same film into the new system.

When choosing a storage medium, there is sometimes an unwarranted concern on the part of a system designer Ñ a fear that selecting microfilm for a given application will preclude its future use in a digital environment. The concern is groundless. Hybrid systems which allow for the integration of microfilmed records and digital systems are already available and in use.