  The current development of digital image correlation, whose displacement
uncertainty is well below the pixel value, enables one to better characterise
the behaviour of materials and the response of structures to external loads. A
general presentation of the extraction of displacement fields from the
knowledge of pictures taken at different instants of an experiment is given.
Different strategies can be followed to achieve a sub-pixel uncertainty. From
these measurements, new identification procedures are devised making use of
full-field measures. A priori or a posteriori routes can be followed. They are
illustrated on the analysis of a Brazilian test.
