Microform: Difference between revisions

Revision as of 15:25, 6 July 2013

Revision as of 22:23, 15 August 2013

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Modern microform scanners utilize 8 bit gray shade scanning arrays and are thus able to provide quite high quality scans in a wealth of different digital formats (CCITT Group IV which is compressed black & white -bitonal, JPG or JPEG which is gray or color compression, bitmaps which are not compressed, or a number of other (some proprietary) formats such as PDF, LZW, GIF, etc.). These modern scanners are also able to scan at "Archival" resolution up to 600 dpi.

For the resulting files to be useful, they must be organized in some way. This can be accomplished in a variety of different ways, dependent on the source media and the desired usage. In this regard, [[Punched card#Card formats|aperture card]]s with Hollerith information are probably the easiest since image data can be extracted from the card itself if the scanner supports it. Some types of microfilm will contain a counter next to the images,; these can be referenced to an already existing [[database]]. Other microfilm reels will have a 'blip' system: small marks next to the images of varying lengths used to indicate document hierarchy (longest: root, long: branch, short: leaf). If the scanner is able to capture and process these then the image files can be arranged in the same manner. Optical character recognition (OCR) is also frequently employed to provide automated full-text searchable files. Common issues that affect the accuracy of OCR applied to scanned images of microfilm include unusual fonts, faded printing, shaded backgrounds, fragmented letters, skewed text, curved lines and bleed through on the originals.<ref name="Arlitsch-Herbert" /> For film types with no distinguishing marks, or when OCR is impossible (handwriting, layout issues, degraded text), the data must be entered in manually; a very time consuming process.

==See also==