16mm microfilm means that the film is 16 millimeters in width. This film is commonly used to film office documents measuring up to 8 = x 14 inches. 35mm microfilm means that the film is 35 millimeters in width. This film is commonly used to film documents that are larger than 8 = x 14 inches and are considered archival.
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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.
A book cradle is a device to support bound volumes. The cradle carefully flattens pages during microfilming to increase image sharpness and reduce shadows during filming without damaging the original binding.
16mm or 35mm film, or a combination of both, is sandwiched between two layers of polyester film, creating a sleeve. There are three to eight sleeves to a jacket sheet. For more information see State Archives Publication #9, Producing High Quality Microfilm, pg. 26.
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.
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.
Background density (Dmax) measures the contrast between the image and the non-image background of the microfilm, and determines the exposure setting to maintain quality control. For more information, see State Archives Publication #9, Producing High Quality Microfilm, pgs. 21 and 24; Publication #11, Introduction to Microfilm, pg.
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.
A blip is an opaque, usually rectangular optical mark located below the image on the roll of microfilm. This blip mark is created by the camera to serve as a retrieval device to locate each exposure on a roll of 16mm film. It is also used for counting images or frames automatically. For more information, see State Archives Publication #11, Introduction to Microfilm, pg.8.