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Digitisation

This document was written, and licensed for publication by MDA.

What is digitisation?

The term 'digitisation' refers to the process of converting objects and documents, such as photographs, manuscripts, printed text and artworks into digital form.

What is the digital life-cycle?

The process of creating a digital version of an object or document is governed by the 'digital life-cycle'. This life-cycle defines the various stages in the creation and use of digitised records, including:

  • Management - involving issues of copyright, long-term preservation and storage
  • Access - the delivery of the image in an appropriate medium
  • Re-use - combining groups of digitised records to create meaningful 'packages', e.g. for learning

Each stage of the life-cycle is associated with specific techniques and standards. The advice here focuses mainly on the creation of the digital record or image.

How does the digitisation process work?

When a document or object is digitised the image is sampled from the original and represented as a grid of dots or 'picture elements' (usually abbreviated to 'pixels').

Each pixel is assigned a tonal value (black, white, shades of grey or colour) which is represented in machine-readable binary code (zeros and ones).

The binary digits, or 'bits', representing the value of each pixel are stored in a sequence by a computer and often reduced to a mathematical representation (a process known as 'compression').

The bits that comprise the image are then interpreted and read by the computer to produce an analogue version for display or printing.

Digitisation equipment types

Digitisation equipment can be separated into two categories: contact and non-contact.

Contact equipment includes hardware like flatbed scanners. Users are required to place the original flat on the scanner in order to get a scanned image.

Non-contact equipment includes overhead scanners, book scanners and digital cameras where images are obtained with little or no contact with the original.

The digitisation of a museum's materials can be done either in-house or sent to an external agency or bureau.

What do I need for basic in-house digitisation?

Basic in-house digitisation will require:

  • A suitable scanner;
  • A powerful computer with adequate memory;
  • System resources including backup and write to media (e.g. CD-ROM, Jaz or Zip drive) capacity;
  • Digitisation software;
  • Staff to run the equipment and manage the digitisation project;

Flatbed Scanners

A flatbed scanner is often the basis of a digitisation project. If you are considering purchasing a scanner shop around as prices vary greatly.

Production-level flatbed scanners usually have either A4 or A3 capabilities.

Transparencies can be scanned on a flatbed scanner if it is capable of sufficient resolution. Most flatbed scanners capable of scanning transparencies will come with an additional transparency adapter.

Transparency scanners are available and generally provide faster and better results than a flatbed scanner with an adapter.

Digital Cameras

Digital cameras can also be used to digitise objects and documents. In a digital camera computer sensors transmit the image to a computer rather than to film. This process is known as 'digital scanning back'.

Choosing the right equipment for scanning your originals should depend on the characteristics of the collection you intend to digitise. The following are basic guidelines:

  • Photographic materials are usually best scanned on a flatbed or a transparency scanner;
  • Bound volumes and oversized flat materials such as maps and plans require a digital camera or an overhead scanner;
  • Mixed media collections may require a combination of scanners in order to scan everything.

What should I look for in a scanner?

Make sure that your museum's requirements match the capability of the scanner that you buy.

Resolution

Resolution is an important factor. Scanners will usually be listed with a maximum optical resolution and an interpolated or software resolution. The optical resolution is the important figure to note.

Where resolution is listed as 600x1200 dpi the maximum optical resolution will be 600.

Software

The software that runs the scanner is also important. The software should be straightforward to use and have an ability to run batch scans. Batch scans enable you to scan a volume of material as a single job. The scanner can then be left to scan the material.

SCSI or parallel port

If you are buying a flatbed scanner find out whether they use a SCSI or parallel port.

If the scanner uses SCSI you will probably have to install a card into the expansion slot of your computer. A scanner that uses the parallel port will plug straight into the back of your computer, which means that you won't have to remove the computer's case.

Choosing a flatbed scanner

When choosing a flatbed scanner there are a number of areas you should consider before buying:

  • What size are your originals?
  • Are they reflective? (i.e. light is bounced off them to capture the image, as in photographic prints)
  • Are they transmissive? (light is passed through the original to capture the image, as in transparencies)
  • What resolution do you want the images to be scanned at?
  • How much material have you got to digitise?

Should we digitise in-house or look outside?

Setting up digitisation equipment within your museum gives the museum itself the value of equipment and trained staff for future projects.

In having it's own digitisation equipment, the movement and treatment of the materials can be closely controlled within the museum.

Your museum may wish to use an external supplier or bureau to do the scanning. By adopting this method the museum has the benefit of using third-party equipment and expertise while allowing the project management to remain within the museum. Using a supplier or bureau also means that the cost of buying and maintaining specialist and expensive equipment is not carried by the museum itself. Your museum should look to an external supplier or bureau:

  • If your museum is unable to digitise material internally
  • If the project is beyond the experience and abilities of the museum staff
  • If there is a large volume of work to be done in a short period of time or where the museum has space, infrastructure or staffing constraints which will prohibit the efficiency and effectiveness of the digitisation project.

Where can I go for further advice and information?

The Technical Advisory Service for Images advise on digital creation, storage and delivery of image-related information.
[ http://www.tasi.ac.uk]

UKOLN is a national focus of expertise in digital information management. It provides policy, research and awareness services to the UK library, information and cultural heritage services.
[ http://www.ukoln.ac.uk]

NOF-digitise page that provides technical advisory support for digitisation projects.
[ http://www.ukoln.ac.uk/nof/support]

MDA provides impartial resources for all aspects of collections information management. For more information please contact: Collections Link - 0845 838 4000.