British LibraryTreasures in full: Caxton's Chaucer
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3. The digitisation - Keio University

The digitisation of the British Library’s best copies of the first and second editions of Chaucer’s Canterbury Tales was undertaken by a team of 14 Japanese men and women, experts in a variety of fields, a professional photographer, bibliographers and IT specialists, all from the HUMI project at Keio University in Tokyo, directed by Professor Takamiya, a specialist in 15th-century English literature, and managed by Masaaki Kashimura.

Books examined before being photographed
Before the books were photographed they were carefully examined by staff from our conservation department to set the appropriate standards for handling.

Keio University also digitised our two copies of the Gutenberg Bible, the two projects amounting to a major benefaction to the British Library, now commemorated on the Library’s tablet of benefactors.

Camera used by Keio University
The camera which the team from Keio used for the Caxton digitsation was a Kodak DCS Proback Plus + Mamiya RZ67 digital imaging system (One shot, 1-CCD, 16M (4000x4000) pixels, 12-bit RGB, IEEE1394 I/F).

All the equipment was flown in from Tokyo, from the single-shot Kodak digital camera, which every three seconds can produce a 16-million pixel image, the battery of computers processing the images, down to stepladders and sticky tape.

As we were dealing with very precious items we of course imposed special conditions of treatment.

The British Library’s Conservation Department specified the degree to which the books could be opened. This meant that the books could not be photographed flat on their backs, and this caused a number of technical problems.

Caxton Chaucer - first edition Caxton Chaucer - second edition
First edition opened at the maximum permitted by our conservation department. Second edition opened at the maximum permitted by our conservation department.

The book cradle
A cradle was specially designed in Japan to our specifications, originally for the Gutenberg Bible project, but modified to suit the exact dimensions of the rather smaller Canterbury Tales.

Fundamentally it consists of three separately moveable parts, which can be gently manipulated so that the book is never open more than at 120 degrees and yet can present to the camera a nearly flat image of each page.

Monitoring the right position
As the British Library did not allow the camera to be above the book, it was a challenge to ensure that the page is parallel to the camera lens. The solution turned out to be mechanical: a square mirror carefully placed on the page and suspended from a central cord. If the square within the camera lens aligns with it, the camera is in the right position.

The structure of the book moves gently as the leaves are turned, so this procedure had to be repeated every five leaves, thereby also allowing adjustments to be made for the slowly increasing distance between the book and the camera.

Final checks
The image once photographed went through a first processing in the camera itself and then through a battery of three laptops.

It was then inserted into the sequence of the other images, given a permanent file name corresponding to the leaf number and a final visual check for clarity and for true colour. It was important that as much as possible of the processing and checking of the image quality took place immediately, for once the team and equipment had gone back to Tokyo it would be nearly impossible to rectify any errors. Each page carries a number which accurately records the printed leaves in the British Library's copy.

The process from shooting to last check took on average 23 seconds. The whole digitisation of the two editions took 10 days. Because the team was generously staffed, the speed was ultimately determined by the physical process of turning the pages and adjusting the book in front of the camera.

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