Whereas archivists are rightly concerned with the preservation of the actual art artefact or object, digital preservation is concerned with preserving the information in it. The point at which art is copied or photographed halts any further information loss from its state at that point in time, even though the original may continue to deteriorate, effectively losing information.

So it is crucial that any copying is not only as accurate as possible at the time, but that the data is collected in such a way that it can be reworked by future technology. Comparative experiments in imaging science show digital capture to be far more colour accurate than the use of photographic film. There are crucial differences between the photographic science (Densitometry) traditionally used to copy artwork, and colour science (Colorimetry). This is discussed further in another article.

Because all colour devices like cameras and scanners have unique colour reponse characteristics, there are three important principles to implement in capturing images for the digital preservation of heritage -

1. Each device should have an International Color Consortium (ICC) profile made of its colour characteristics.

2. This profile should be included in the copy image's metadata (information about the image information), to enable validation with future technology.

3. What is known as "raw" image data should be captured.

The application of colour science in digital preservation is slow to penetrate the archivist community, and new working methods are needed in digitisation projects. Current best practice guidelines by archivists in the UK refer to documents dated as long ago as 1993, long before the advent of modern imaging science.

In 2005, a survey seeking benchmarking practice was completed by the Rochester Institute of Technology, one of the world's main research bases in artwork measurement and reproduction, in conjunction with The Image Permanence Institute. In a survey of 52 major American museums' art reproduction practices, they found a significant lack of understanding of colour science principles and practice.

Since many of the scientists that wrote this report sit on ISO committees dealing with photographic topics, Cumbria Picture Library feels that we are heading for an ISO standard for art reproduction, and also that this is likely to influence funding bodies in awarding digital preservation projects.

One of the major recommendations of the benchmarking document, was that a range of skills was needed in art reproduction - in particular a colour scientist and an art historian. The reason for the latter skill was to inform about the art regarding it's topographic or surface characteristics, since the art is regarded photographically as three, rather than two-dimensional.

For this reason, Cumbria Picture Library is putting out a call for a museum or institution involved with archiving to collaborate on a digital preservation project, and be involved in pioneering work in this area. Archiving a photographic collection is one possibility, but photography of fragile artefacts is another.

Tony Riley

Last revised Jan 2007