Microfilm, microfiche and aperture cards are all mediums for storage and retrieval of specifications and documents. They are similar in that they all use 16mm or 35mm microfilm. The film consists of an emulsion embedded on a substrate of cellulose or plastic. The image is created by a photographic process and images can be made in black and white with various resolutions. The image on the film is typically about 1/100th the full resolution size. Microfilm typically comes in reels. Microfiche comes in sheets (typically 4” by 6” in size) and has multiple images.
Aperture cards are normally punched cards with a rectangular opening that contains a single image on microfilm. The aperture cards brought together 2 technologies used in the mid 20th century: Punched cards and microfilm. Microfilm was first commercialized in the 1920’s by a banker named George McCarthy. The original purpose was to make permanent records of bank transactions.
Punched cards or Hollerith card were invented in the late 1800’s and were used as a way to store data for the US government. The card consists of columns of punched holes, where the position of the hole in the column corresponded to a number (0-9). The code could be read with a card reader that would automatically determine the position of each punched hole on the card. Because they could be rapidly read and easily handled by automation, punched cards became the primary method for computer programming back in the late 1960’s and early 1970’s
The first patent for an aperture card was filed on January 29th 1963, and a subsequent patent was issued on October 19th 1965 that contained a number of improvements over the original design.
Aperture cards had or have a number of advantages over microfilm and microfiche. First, indexed or eye-readable information can be place alongside the image on the card. This allows for rapid retrieval of a specific document, whereas film alone required some sequential scanning to find the corresponding image. Secondly since each card contains only a single image, sharing or duplication of specific information is much more convenient. Thirdly, information such as document number, category, date issued etc could not only be read by a card reader but the information could be printed on the card. Hand written notes can also be added to enhance indexed information. Someone can easily determine what was on the aperture card without using a film reader. Aperture cards can also be color coded, giving the user another level of visual categorization.
Aperture cards were more expensive to create than microfilm and microfiche. They also take a bit more physical space to store and there is probably a greater chance of an aperture card getting lost or damaged than microfilm.
Aperture cards were ideal for drawings or specifications because not only do you have a convenient way to view the document, but aperture cards provides easily read indexing for fast retrieval. Also they can be duplicated and transported as single image units. A lot of manufacturing firms, government agencies, architecture firms and engineering companies used aperture cards to store media.
Aperture cards have essentially been made obsolete by digital technology. Storing the specification image along with the pertinent document data can be done far more effectively with computers. However there are still a lot of businesses and organizations that have aperture cards. The image on the card can last over 500 years and the punched cards are durable and easily duplicated, so there is little risk of an aperture card “wearing out”. Many organizations are scanning aperture cards and converting them to images or searchable pdfs, as digital format is more convenient and cheaper to store than aperture cards.
Microfacs has the technology that can automatically scan the film on the aperture card and read the punched card to automatically create an indexed digital file. Some aperture cards don’t have punched holes, or some of the information is hand written on the card, so manual indexing may be needed in those cases.