A recent, and what seems like a natural evolution, of photography has been for
quantification. With modern cameras that can more realistically depict what is visible, it is
possible to measure change using (digital) photography. This chapter considers various
examples of the application of photography in the measurements of surface colouration
(soiling) and the decay of weathering forms. Techniques developed by the first author are
presented, and a case study on the application of the O-IDIP method is presented to convey
photographic surveys for the quantification of stone surface colouration associated with
biological colonisation on a string course in central Oxford.
Keywords: Calibration, CIE Lab, decay mapping, DMAP approach, histogrambased
colour measurement, O-IDIP method, surface colouration.