Aperture card

An aperture card is a type of punched card with a cut-out window in which a chip of microfilm is mounted. Such a card is used for archiving or for making multiple inexpensive copies of a document for ease of distribution. The card is typically punched with machine-readable metadata associated with the image microfilm, and printed in the card for visual identification. The microfilm chip is most commonly 35mm in height, and contains an optically reduced image, usually of some type of reference, such as an engineering drawing, that is the focus of the archiving process. Aperture cards have several advantages and disadvantages when compared to digital systems. Machinery exists to automatically store, retrieve, spell, duplicate, create, and digitize cards with a high level of automation. While many aperture cards still play an important role in archiving, their role is being replaced by digital systems.

Usage

Aperture cards are used for engineering drawings from all engineering disciplines. The US Dept. of Defense Ounce of Extensive Use of Aperture Cards, and some are still in use, but most data is now digital. [1]

Information about the drawing, for the drawing, could be both punched and printed on the back of the card. With the proper machinery, this allows for automated handling. In the absence of such machinery, the cards can still be read by a human and a light source.

Advantages

Aperture cards have, for archival purposes, some advantages over digital systems. They have a 500-year lifetime, they are human readable, and there is no expense or risk in converting from one digital format to the next when computer systems become obsolete. [2]

Disadvantages

Most of the disadvantages are related to the well established differences in analog and digital technology. In particular, searching for given strings within the content is considerably slower. Handling physical cards requires proprietary machinery and optical film processing takes significant time.

The use of microfilm cameras and the high contrast properties of microfilm can also be used to reduce the size of the film (36x or greater). Faded drawings or those of low or high contrast may be lost.

In common with other forms of microfilm mis-filing cards after use, especially in large archives, results in the card being for all intents and purposes lost forever unless it is later found by accident.

Aperture cards created from 35mm roll film mounted on blank cards. Bending the card can cause the film to detach and excessive pressure to a stack of cards can cause the mounting glue to ooze creating clumps of cards that will feed through duplicators and other machinery or poorly at all. Feeding a de-laminated card through machines not only risks but also risks jamming or damaging the machinery.

Machinery

A set of cards using a card sorter . Machines are now available that scan aperture cards and produce a digital version. [3] Aperture card plotters are machines that use a laser to create the image on the film. [4]

Conversion

Aperture cards can be converted to digital documents by scanning equipment and software. Scanning can allow for significant image cleanup and enhancement. Often, the digital image produced is better than the visual quality available prescan. [5]

References

  1. Jump up^ Aperture cards (Archived Copy)
  2. Jump up^ LoTurco, Ed (January 2004). “The Engineering Aperture Card: Still Active, Still Vital” (PDF) . EDM Consultants. Archived (PDF) from the original on November 28, 2007 . Retrieved October 10, 2007 .
  3. Jump up^ For example, this aperture card scanner fromOce ‘
  4. Jump up^ For example, this aperture card plotter fromWicks & Wilson Archived onJune 27, 2006, at theWayback Machine.
  5. Jump up^ Bryant, Joe. “Aperture Card Scanning” . Micro Com Seattle . Retrieved 17 March 2015 .

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