Monday, March 23, 2015

Microfilm technology

Image technology

  • The storage of documents or other data that includes text, graphic, tables, and pictures
  • 3 Image Technologies
    • Facsimile
      • transmits information
    • Storage and retrieval of images, text, graphics and pictures
      • Optical Disk
      • Micrographics
Microforms
  • Any medium that contains miniature or “micro” images
    • Microrecords – records stored on microforms
    • Micrographics – procedures for creating, using, and storing microrecords
  • Types
    • Roll film
      • most economical and frequently used
    • Microfiche
      • fiche with reduction ratios of 90X or greater known as ultra fiche
    • Jackets
    • Aperture cards
    • Nonstandard microforms
    • Computer input microform

(Microfiche)

(Aperture card)
 (Microjacket)
(Microfilm)

Microform procedures and equipment
Each step in using micro-records requires special procedures and equipment:
  • Filming
  • Coding
  • Processing
  • Inspecting
  • Duplicating
  • Reading
Filming
  • Document pre parathion
    • Remove all paperclips and staples
    • Mend torn papers
    • Attach small papers to standard size paper with transparent tape or rubber cement
    • Remove unnecessary attachments, e.g. envelopes, routing slips, duplicate copies
  • Camera film
    • Standard camera film uses silver halide emulsion to capture detail (often called silver film)
  • Image size
    • Reduction ratio compares film image size to original document size
    • Reduction ratio of 24x = image 1/24th size of original document
  • Image orientation = positioning of images
    • Cine, comic, duplex, duo, duplex/duo
  • Types of cameras
    • Rotary (high volume)
    • Planetary (flatbed)
    • Step & Repeat (flatbed with overhead)
    • COM Recorder (records electronic from computer optical machine to microform)
Coding
  • Microforms during filming may be coded/indexed for automated retrieval
    • Flash Targets
      • Divides roll into information batches
    • Bar Coding
      • Requires additional equipment and space
    • Odometer Indexing
      • Indicates distance of each image from beginning of roll
    • Blip Coding
      • Predominant method
      • Place rectangle beneath each image to identify; must be indexed
Processing
  • 3 types of processing
    • Deep tank
    • Roller transport
    • Straight film path
  • Reversal processing
    • Positive/Negative Polarity
    • Developed for use with COM (computer output microform)
  • 4 factors that affect developing
    • Temperature of the developer
    • Time film is in the solution
    • Condition of the developer
    • Agitation of film
  • The higher the temperature of the developer, the less time the film is required to be in the solution
Inspecting
  • Light box
  • Density
    • Numeric obtained through light background
  • Resolution
    • Sharpness of the image
Duplicating
  • Duplicating process
  • Types of copy film
    • Silver Print
      • easy to use
      • expensive
    • Diazo film
    • Vesicular film
      • cheaper
      • consider using if not for long-term use
Advantages of microforms
  • Floor space savings
  • Fewer storage cabinets = reduced equipment costs
  • Improved file integrity
    • Images cannot be separated or misplaced like sheets of paper can
  • Improved productivity
  • Fast retrieval from automated systems
  • Vital archival records protection
  • Low-cost reproduction and duplication
  • Admissible (in most cases) as evidence in court

Limitations
  • User resistance
  • Cost of purchasing and operating
  • Turn-around time need to produce micro-images
    • Original records inaccessible during preparation and filming
  • Impractical for records that are frequently modified
Future of microforms
  • Microfilm takes up about 2% as much space as equivalent paper records
  • Permanence of from 100 to 500 years
  • Can be read with human eye; not totally dependent on specific hardware/software for access
  • Legality is well established

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