a method and apparatus for performing surveillance comprising : imaging , at a first frame rate , an area to produce images ; detecting , using the images , a feature of interest within the area ; determining a region of interest , the region of interest corresponding to a region within the area in which the feature of interest will be located at a later time - step ; and , at the later time - step , using the region of interest , imaging the area such that images of the region within the area in which the feature of interest is located are produced at a second frame rate , while images of the rest of the area are produced at a third frame rate , the second rate being different to the third rate .