What are Aperture Cards and their types, How are they used? Aperture cards are an affordable way of storing or archiving multiple copies of documents, engineering drawings and maps , and photographs to ease access, distribution, and long-term storage. Aperture cards were introduced in 1943 and used by US military agencies to capture and archive photographs of strategic value and other important documents. An aperture card is basically a holerith card with a cut-out window where a chip of 16mm or 35mm microfilm is mounted. This microfilm mounted consists of an optically reduced image of a confidential document such as an engineering drawing, maps or newspaper pages. The aperture card can be viewed only on a specialized card reader which interprets the metadata on the punch cars and enlarges the film for easy viewing. The use of microfilm has been widely popular for archival purposes as well as a solution to bulky, expensive storage of print materials. Over the years, improved film, better readers and viewers, high-tech reader-printers, and portable readers also helped drive the popularity of microfilm storage options. Today, though microforms are still used to preserve and store documents, businesses are opting to scan and digitize their microfilm and microfiche cards. This allows content to be easily viewed on computers and shared and stored digitally. Different Types of Aperture Cards Available •
Conventional aperture cards – A conventional aperture card (82.5mm x 187mm) have a microfilm mounted on a window provided on the card with dimensions of approximately 50mm x 40mm that will light to fall on the microfilm image, allowing the data contained in it to be read.
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Duplicards – These are aperture cards with duplicating film pre-mounted in them, but unexposed. Of dimension 82.5mm x 187mm, the duplicard consists of a diazo emulsion microfilm and is used for making a copy of an original aperture card for future use.