Aperture cards are punched cards with a microfilm containing data such as drawings, while the punched card includes details about the data. They were designed for archive use but have been largely replaced by digital systems. They take up less space than full-sized blueprints and drawings but require manual activity. Some archives have been converted to digital format, but opening card blanks are still available for personal use.
An aperture card is a punched card that includes an opening into which a piece of microfilm is inserted. Microfilm contains data such as a drawing, while punched card includes details about the data. Aperture cards were designed for archive use in a wide variety of applications, and some are still used in this sense today. For the most part, however, digital archival systems have replaced the aperture card.
Some examples of items that can be mounted on an aperture card include blueprints, technical drawings, and microfilm of newspaper pages. The size of the film varies depending on where and when the film was produced. The card, marked in the Hollerith code, usually also has human-readable information so that the card can be easily identified.
A specialized card reader is required to view an opening card. The card reader can interpret the metadata on the punched card and enlarge the film so it can be easily viewed. Card readers may include the ability to sort and catalog a large collection of opening cards, allowing people to manage a large archive.
The distinct advantage of an opening card from an archival perspective is that it takes up much less space than full-sized blueprints and drawings, along with accompanying information. The standardized size and shape also make the opening cards easier to memorize when compared to the original designs. For example, a county records office may file deeds and plans in a small room when they’re on opening filings, requiring a much larger space for the original documents.
The downside, of course, is that opening cards still take up space and require some manual activity, unlike digital information. With a digital filing system, information can be cataloged in various ways and instantly recalled whenever needed. Digital systems, however, can degrade data if it becomes compromised, and it can be costly to replace systems as new technologies are developed.
Substantial archives of opening cards have been converted to digital format for convenience in some regions. The original cards can be kept or discarded once it is clear that the digital system is functional. For people with a particularly burning interest, opening card blanks are still available, allowing people to create new opening cards. Such papers are mostly used for personal interest rather than institutional storage, because digital technology has so many clear advantages, making it a preferred choice.
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