The principal examiner determined reference points and took measurements from the full set of photographs and radiographs (76 feet) on 2 separate occasions 2 weeks apart. That is, on each measurement occasion, each image was independently marked up and an independent measurement produced. To minimize test-retest bias and to ensure that the examiner was unable to recall previous observations, no reference was made to the data or images in the interim. All the photographic measurements were taken first in a single measurement session, followed by the radiographic measurements, such that no direct comparison could be made between the radiographs and photographs of individual subjects. A second examiner measured a subset of radiographs and photographs (40 feet), following the measurement protocol described above, on a single occasion. Both the principal examiner and second examiner were podiatrists with 3 to 4 years of clinical experience.