PRINCIPAL POINT BEHAVIOUR AND CALIBRATION PARAMETER MODELS FOR KODAK DCS CAMERAS

Digital still cameras have been widely adopted for close range photogrammetry and machine vision applications. Due to the advantages of onboard storage of digital images, portability and rapid data processing, digital still cameras are rapidly becoming standard equipment for measurement tasks such as industrial metrology and heritage recording. As for any metric application, the accuracy of the derived object data is dependent, amongst many other factors, on the accuracy of the camera calibration. For the vast majority of photogrammetricapplications, use of the simple case of a block invariant calibration model comprising the primary physical parameters, including the principal point position, is sufficient.However, cameras designed for photojournalismand domestic use, such as the Kodak DCS420 and 460 cameras, are well known for their calibration instability because the design is based on a 35 mm SLR camera body. In particular, previous research has shown that the principal point location is prone to movement during normal handling of the camera, due to the mounting mechanism of the CCD array. This paper reports on an investigation of the physical behaviour of the principal point location and compares different calibration parameter models for the Kodak DCS420 and DCS460 digital still cameras. F RONTISPIECE . A unique remote application of digital photogrammetry used as an inspection tool during the first fully remote shutdown at JET Joint Undertaking, the European Union fusion research project based at Culham, Oxfordshire, England. An article by Macklin et al. describes the work elsewhere in this issue of the PhotogrammetricRecord.