1. A method of operating an image processing system, the method comprising: generating a plurality of respective models from identified objects in a first video, wherein said respective models comprise descriptors of parts of said identified objects; evaluating an ability of each of the plurality of respective models to identify other objects in said first video when said other objects are similar to a respective identified objects from which said plurality of respective models was generated; and identifying at least one preferred model from the plurality of respective models based on the evaluating step.