1. A computer-implemented method of image retrieval from a target image collection, the steps performed by a computer system and comprising: segmenting a query image into two or more bands; obtaining weighted colour histogram vectors for the two or more bands in the query image; obtaining weighted colour histogram vectors for two or more bands in a target image; and, determining a distance measurement between the query image and the target image using the weighted colour histogram vectors from corresponding bands in the query image and the target image; wherein the distance measurement (D) between the query image (I q ) and the target image (I m ) is determined using: D ⁡ ( I q , I m ) = ∑ i = 1 N ⁢ ⁢ w i · d i ⁡ ( x qi , x ni ) where: d i is the individual distance measurement for selected corresponding bands between a colour histogram x q of the query image and a colour histogram x n of the target image; and w i is a weight applied to the i th colour histogram x.