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1.1 Terms of reference

1.2 Aims and objectives

1.1 Terms of reference

Developments in image capture technology allow developers of multimedia applications to incorporate source material of varying physical characteristics. However the multimedia developer drawing up a specification for a capture system is faced with a bewildering choice of equipment for which there is little comparative information on the relationship between equipment specification and captured image quality. This report provides guidelines for decisions on the choice of appropriate capture pathways within the context of higher education.

Source material may vary from original objects such as biological specimens through hard copy sources like manuscripts, books, maps, photographic sources such as transparencies and film, to electronic sources like videotapes or video discs. There are a number of devices which can be used to capture images of the source material, although not all images can be captured by each device.

Six stages of image capture and processing were identified as follows:

  1. Selection of source material
  2. Initial capture (photographic or analogue)
  3. Secondary capture (digital)
  4. Manipulation in a photo re-touching software package (e.g. Adobe Photoshop)
  5. Compression
  6. Storage
Use of the term 'analogue' refers to electronic image capture where signal amplitudes are continuously variable. 'Digital' refers to signals recorded in bits, that are either 'on' or 'off'. The terms of reference for the project were to address the effects of various capture processes on image quality, stages 2 and 3 above. The project did not systematically address the effects of subsequent software manipulation, stage 4, or of compression after digitisation, stage 5, although both can affect the quality of the final displayed image.

In specifying a capture system it is necessary to achieve sufficient image quality to meet the required teaching/learning need within defined budgetary constraints. Quality as far as image capture is concerned is monitored by assessing three distinct facets of each image:

  • Spatial resolution (sharpness)
  • Colour (faithfulness to original)
  • Contrast ratio (range of half tones).
The acceptability of a captured image is determined by the combined effects of these three facets.

As equipment choice is likely to be constrained by budget, the implications of two cost scenarios on the quality of image capture were assessed. The two systems were chosen as follows:

  • Centralised Service Model: purchase of higher cost equipment justified by high throughput and intensive use.
  • Departmental Model: in this scenario the facility is only likely to be used intermittently and consequently the purchase of high cost equipment is unlikely to be justified.
In addition, these two budgetary scenarios were compared with results obtained from the use of the Kodak PhotoCD system, for which no investment in electronic capture equipment by the institution is required.

1.2 Aims and objectives.

The aims of the project were to evaluate a range of hardware and associated software options for the capture of images for two equipment cost scenarios as defined above, and to draw up guidelines for the selection of appropriate systems for image capture by developers of multimedia applications in higher education.

The objectives were to identify:

  • types of source material required as digitised images by developers of multimedia applications for higher education
  • optimal pathways for capture of images bearing in mind feasibility, quality and cost
  • the implications of two budgetary scenarios for hardware and associated software on the quality of the captured images.

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