High resolution colorimetric imaging of paintings

Description/Abstract

With the aim of providing a digital electronic replacement for conventional photography of paintings, a scanner has been constructed based on a 3000x2300 pel resolution camera which is moved precisely over a 1 metre square area. Successive patches are assembled to form a mosaic which covers the whole area at c. 20 pels/mm resolution, which is sufficient to resolve the surface texture, particularly craquelure. To provide high colour accuracy, a set of seven broad-band interference filters are used to cover the visible spectrum. A calibration procedure based upon a least-mean-squares fit to the colour of patches from a Macbeth Colorchecker chart yields an average colour accuracy of better than 3 units in the CMC uniform colour space. This work was mainly carried within the VASARI and MARC projects, funded by the European Commission's ESPRIT programme, involving companies and galleries from around Europe. The system is being used to record images for conservation research, for archival purposes and to assist in computer-aided learning in the field of art history. The paper will describe the overall hardware and software design. The theoretical basis for the colour calibration methodology is described. The mosaic assembly procedure and some of the associated image processing routines developed are described. Preliminary results from the research will be presented.