Image data processing method and apparatus

A method of processing image data generated using an image capture device comprising a lens, the method comprising, generating metric data for a plurality of regions of an image, the data representing a plurality of focus measures for each region generated at a plurality of lens positions, processing the metric data in order to cluster regions into at least one group on the basis of their respective focus measures, and determining a lens position for a group corresponding to a position of true focus for the group.