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Storage and Preservation

What are the different roll lengths for microfilm? What are the advantages and disadvantages of each roll length?

16mm microfilm comes in rolls that are either 100 ft. x 5ml thick, or 215 ft. x 2.5 ml thick. 35mm microfilm comes in 100 ft x 5ml thick rolls.

Advantages of using 215 ft.- length rolls of film are that it doubles the number of document images that can be exposed on a roll, and the film roll can fit onto the same spool as 100 ft. film.

Disadvantages of using 215 ft.- length rolls of film are that it takes longer to retrieve an image at the end of the roll, and that because the film is thinner, it has a tendency to tangle into knots.

What is COM?

Computer Output Microfilm is microfilm produced directly from a computer file. COM produces high-quality microfilm, usually in 105mm microfiche format. It can also produce 16mm, 35mm and 70mm roll film.

What's the difference between a rotary and planetary camera?

A rotary microfilm camera photographs documents while they are being moved by a transport mechanism. The film is moving at the same speed as the document during exposure.

A planetary microfilm camera, also known as a flatbed camera, photographs documents in a stationary position during exposure. The film is also stationary. Image quality from a planetary camera is much higher than from a rotary camera.

What is a resolution chart?

A resolution chart is a technical chart containing twenty-six sets of detailed horizontal and vertical lines of varying sizes and specific spacing. It is used to test the ability of the microfilm to record fine detail so it is readable. There are five charts to a resolution target, and these charts are located at the center and four corner points of the target. For more information about resolution, see Archives Publication #9, Producing High Quality Microfilm, pg.

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