For high contrast materials such as books, newspapers, some maps and drawings, preservation-quality microfilm can be generated from high quality digital images, and high quality digital images can be generated from preservation-quality microfilm. For existing microfilm collections, it appears to be more cost-effective to scan from microfilm than from original materials.

For collections that have not been microfilmed, it appears to be more cost-effective to scan materials, then use the images to create computer output microfilm (COM). However, because many institutions have experience with creating preservation-quality microfilm, it may be easier for them to microfilm materials first, then send the microfilm to a service bureau for scanning.

If microfilming is done on-site, there is an additional advantage in that the library or archive will not have to send original materials out to a service bureau. The disadvantage to his method is the reduced tonality and resolution limits of earlier microfilm originals. Moreover, some microfilm scanners may not have the resolution to produce scans of adequate quality.

Whenever possible, the archival file format you choose should be open rather than proprietary. Open means the format is supported by many groups and standards organizations, such as NISO or ISO. Individual companies own proprietary files. The advantage of open file formats is that they are supported by many communities and most likely will not lose support without the approval of the groups that support them.

Most institutions presently save their archival images as uncompressed TIFFs. The display format most institutions choose for photos is JPEG because it holds more color information than GIF. For printed, text-based materials, GIF is usually the better choice because it displays crisper edges, providing better reading of printed text. Display formats for manuscripts vary. For manuscripts with lots of color in them, or when details of the paper or other support are important, JPEG will usually be your best choice

For blue or black writing on white paper, GIF will suffice. JPEG and GIF both use compression to reduce the size for transport across networks. JPEG uses a lossy compression which strips redundant bits form the original file to reduce its size. When using JPEG, one should be careful to avoid over-compressing the file to avoid artifacts. GIF is a lossless format; it takes care not to lose file data.

Most thumbnails are either JPEG or GIF. Since the function of thumbnails is purely for identification, color information is not as important as with display or archival files. A new standard, JPEG2000, promises to combine all the functions of archival, display, and thumbnail into one file format. JPEG 2000 uses wavelet compression, a method that allows for higher compressions of image files while maintaining better image quality.

A JPEG 2000 file can be compressed to twice that of a JPEG file while maintaining the same image quality. JPEG files can be compressed using either lossless or lossy compression. Metadata can be stored with JPEG 2000 files. However, I would proceed with caution. With JPEG 2000, all versions of the digitized image are bound into one compressed file. Compression adds another level of complexity that may increase the difficulty of regaining the ability to read the file should it fall into disuse in the future. Uncompressed TIFF files, on the other hand, consist of bitmaps of pixels that are much simpler to interpret.

When a decision has been made to film records, another decision needs to be made regarding which format to use: microfilm or microfiche. Both have advantages and disadvantages. Microfilm comes in rolls 100 feet long (200 feet for thin film). Once filming is completed, adding a new frame (page) somewhere in the middle of the film is difficult, so if you have files which are added to frequently, microfilm may not be the best option. Microfiche (105mm film divided into "cards") allows additions more easily because extra fiche can be filed behind the first, keeping data intact. Each fiche holds approximately 90 pages of information. Microfiche is somewhat easier to use and to find information quickly, though microfilm can be set up so that users can move to bookmarks (called "blips") quickly anywhere on the film reel. This does require film reader machines to utilize the "blip" system, however. Generally speaking, microfilm is less expensive than microfiche. Microfiche tend to get misplaced more easily than film, too.

Benefits of Microfilming

There are various reasons for microfilming records. One of the most important is for the preservation of information. Microfilm is recognized as durable medium for permanent records, with an estimated lifespan of more than 500 years when properly manufactured, processed, and stored. Records whose original format has intrinsic value would also benefit from filming in order to save wear and tear on the original. If the records do not have intrinsic or even permanent value, but are used frequently, microfilming can still save on wear and tear.

Micrographic technology has been around for more than 70 years, so there is a well-developed set of standards that, when followed, assure high quality, longevity, and compatibility. These standards are set by organizations such as American National Standards Institute (ANSI ) and the Association of Information and Image Management (AIIM).

Microfilming provides security of information vital to the operation of an office. If records are microfilmed and the film is stored off-site, the data will be available even if the original paper is destroyed or lost. The need for space can also be a factor since a roll of microfilm can hold from 900 to 6000 pages. The cost of storing paper in a records center balances the cost of filming after approximately twenty years. Storing paper in an office setting (which is very expensive) would justify the cost of filming well before the twenty-year mark.