Digitising the collection

The production process was the heart of the Insight project. Since delivery systems come and go, the main investment emphasis of Insight needed to be on capturing images and creating text in a way that would be of long-term value. Images are stored in standard compressed formats online, and the masters are archived for use in future delivery systems, or for output in other formats such as print.

The project set ambitious workflow goals of capturing around 150 works each day, and in order to achieve this all aspects of the working process required careful planning. A specialist team was recruited and a studio established in the Clore Wing at Tate Britain. The studio is comprised of two rooms, one set up for Imaging and the other for Indexing.

Insight production was supported by a customised Image Management System (IMS) supplied by iBase Media Services Ltd, still in use and expanding to become a Digital Asset Management System. Software was developed to offer several different interfaces to support indexing, image capture and processing, conventional photography, copyright and workflow management.

The Imaging team included an Imaging Co-ordinator and Imaging Assistant. With production in full swing, many works passed through the imaging studio every hour and careful track was kept of their progress.

The camera used to capture works on paper was made up of a Leaf Volare digital back and a Nikon lens. This camera is still used in the photography department. Works are placed on a copy-stand that can travel up and down to capture A0-sized works down to postage stamps.

A specialised transparency scanner was also used to convert the photographs to digital format and they were scanned at a resolution as close to that of the digital camera as possible. After the scanning process, the transparencies were imported to the IMS and processed in line with standard procedures.

The Image Management System contains basic image processing tools, which can be quicker than the alternative of routing the images through Adobe Photoshop before import. Once in the database, adjustments can be made to the colour, tone, orientation and overall look of the images. The images from the camera need little if any changes made, other than some cropping. Digital cameras are very objective and generally produce images very true to the original.

However many of Turner’s sketches are in reality so difficult to decipher that image enhancing technology has been employed to artificially strengthen these very faint works. These causes of these faint works asre as follows:

• The sort of very fine and light pencil that Turner used is vulnerable to fading and this has happened to a number of works.
• The 1928 flood, when the Thames burst its banks affecting storage areas in the Tate building at Millbank, caused enough damage to literally wash out some of the sketches and sketchbook pages.
• A small percentage of Turner’s output was executed on blue textured paper, which has the effect of disrupting the pencil marks and rendering the drawing difficult to see.
• A percentage of the works consist of pencil drawings on top of washes and the pencil becomes hidden within the wash.

To produce the best possible result, the Institute for Image Data Research at the University of Northumbria was commissioned to do the work, in close liaison with key Insight Imaging staff. The following procedure was adopted:

• The images were first sorted into sets based on differing paper colours and textures. Content Based Image Retrieval (CBIR) technology was employed to assist with this task. The software, a proprietary package, greatly speeded up the task and contributed to the success of the rest of the process.
• A total of ten different colour groups were identified, to which custom processes could be applied.
• The processes were constructed using Adobe Photoshop functions.
• The functions chosen made changes to the balance of colour and tone as well as adjusting shadows, midtones and highlights in the images, with the result of clarifying the pencil marks.
• The processes were worked out by careful collaboration between the IIDR and Insight Imaging staff until the best set for each colour group was confirmed.
• After a period of intensive experimentation and adjusting, the set of processes was applied to the appropriate colour set in Photoshop at the Institute. The procedure was automated to allow batches to be processed overnight.
• All the images were checked manually, by staff in IIDR, for any problems after each batch was processed, using proprietary software, allowing for instant comparisons between the original and enhanced images.

Each image was examined carefully for quality and for any possible faults such as incorrect orientation, strange effects or wrong catalogue data. If the image passeed, it was be signed off ready to be picked up by the server and fed daily to the delivery systems.

The Insight team also worked in partnership with a range of different technologies to pilot innovative new special imaging treatments for more effective representation of three-dimensional and other challenging works.

There is little gain in digitising all these images unless they are indexed for retrievability via subject search. The aim is to provide new routes into the collection in addition to the traditional paths of artist- or title-based retrieval, which assume knowledge of the collection many visitors do not have.

Indexing is the second production stage, since it is carried out from on-screen images to avoid unnecessary handling of the originals. The team index around 150 items per day and this demanding workflow requires that the indexing process achieves a balance between covering large numbers of works and offering a meaningful level of information for each individual work. Workflow rates are very dependent on the type of work being indexed, since the diverse collection includes both straightforward representational works and highly complex works with perhaps complicated iconographical or topographical detail.

The index has been devised from scratch, but drew heavily on the pre-existing public information index built up by the Information Desk in response to subject enquiries from gallery visitors. Standard classification systems, such as ICONCLASS, as well as other systems employing subject-based retrieval also informed the structure of the index, along with extensive consultation with key Tate staff across a range of departments. The resulting index is quick to apply and completely focused on the needs of this collection.

Once indexed, the work is assigned one of three sign-off statuses that reflect the level of indexing in terms of available interpretative information. A group of representatives including Curators, Education and Picture Library staff regularly receives samples of indexed works to check and approve, ensuring the integrity and consistency of approach. Once comprehensively indexed, the future potential of the index is enormous in terms of providing thematic hooks into the Tate collection.

The Image Management System automatically gathers the metadata on record status, recording all who/what/when details at each production stage, as well as assisting with photographic records and copyright management. The system also provides a number of management information reporting tools to track and analyse workflow progress.

Tate’s photography department has almost completely moved over from film to digital production, and has been implementing a strategic conversion to achieve 100% digital capture and output by the end of 2009. This has involved a significant investment in digital hardware as well as embracing new digital working practices.

Leading on from the Insight project, digitisation of the collection continues and most of all new photography is now carried out using digital equipment. Many transparencies come to the gallery from external sources such as artists, and are scanned along with existing Tate transparencies on new Imacon film scanners which are capable of producing very high resolution scans suitable for high-quality reproduction.

Many aspects of the original Insight project remain embedded within the photography workflow. For instance the Leaf Volare camera is still used on the copy-stand to capture works on paper. The Image Management System (IMS) has expanded, with new users and software upgrades turning it into a robust digital asset-management tool.

The digital workflow ensures that a wide range of image formats and sizes are captured and stored. These include the master image which is archived at its original size and format; and it is from this image that almost all the images that appear on the website are made. The IMS holds many useful sizes and formats and it is part of the photography department’s job to supply these images on demand to the rest of the organisation.

One exciting innovation has been the adoption of high-end digital cameras producing RAW file sizes up to 200MB. These cameras are made by Hasselblad and the photography department has acquired a number of these cameras to make up the backbone of their digital capture activities. The images captured by this equipment are of superb quality and are an extremely valuable resource. Standardised file sizes have also increased since the Insight project and currently stand at a maximum of 100MB 8 bit tiff required for fine-art reproduction purposes and the digital picture library. In addition, Nikon medium-resolution cameras have been introduced with the ability to produce RAW files of up to 35MB, which are suitable for a range of uses including press, portraits and installation photography.

Digital preservation is very important at Tate. Master images are archived onto DVD and a version of the archival image is also kept on a secure server, allowing easy access. Two copies of the DVDs are kept; one on-site at Millbank and other in a cold store at the National Gallery in Trafalgar Square . Preservation-quality materials are used including special jewel-case inserts and acid-free storage boxes.

Digital techniques have extended to most of the activities carried out in the Photography department such as infra-red and ultra-violet photography for paintings and sculptures which are used as part of the conservation process and can be invaluable in revealing detail invisible to the naked eye. X-ray is still carried out conventionally but research is being carried out with a view to converting to digital by the end of 2009. There is also a substantial database building up of non-art images. These include images of the buildings, construction projects and artists’ portraits which are to be made accessible to staff via a Tate Net IMS interface in 2008.

Production of photographic prints will be required for the foreseeable future and a conventional darkroom still operates, however this is to be replaced with a digital darkroom also during 2008.