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Technical-system integration Technical-how scanners work

6B. Technical Infrastructure: IMAGE CREATION

Key Concepts

how scanners work
scanner types
image processing




A dazzling array of devices that start the digitization chain now beckon the prospective digital imaging initiative. Note: We use the term scanner to refer to all image capture devices, including digital cameras.

Ask some key questions about any scanner you might consider.

  • Is this scanner compatible with my documents? Can it handle the range of sizes, document types (single leaf, bound volume), media (reflective, transparent), and the condition of the originals? For additional details on matching a scanner to a particular set of document specifications, see Appendix A "Assessing Document Attributes and Scanning Requirements" of The RLG Worksheet for Estimating Digital Reformatting Costs and Don Williams, Selecting a Scanner.
  • Can this scanner produce the requisite quality to meet my needs? It is always possible to derive a lower quality image from a higher quality one, but no amount of digital magic can accurately restore detail that was never captured to begin with. Factors to consider include optical (as opposed to interpolated) resolution, bit depth, dynamic range, and signal-to-noise ratio.
  • Can this scanner support my production schedule and conversion budget? (Pay attention to throughput claims—often a major factor in scanner cost.) What are its document handling capabilities? Its duty cycle, MTBF (Mean Time Between Failure), and lifetime capacity? What kind of maintenance contracts are available (on-site, 24-hour replacement, depot service)?

Scanner specifications can be difficult to interpret and often lack standardization, making meaningful comparisons impossible. The RLG/DLF guide, Selecting a Scanner examines scanner specifications related to image quality and can help the reader see past the marketing hype that is commonplace in the industry.

As you read through the details of available scanners, keep in mind that most scanners were designed for large markets such as the business and graphic arts segments. Few were designed to accommodate the specific needs of libraries and archives. Your goal will be to find one that best fits your needs with the fewest compromises.

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Technical-system integrationTechnical - how scanners work

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