1. A camera-recorder apparatus comprising: (i) an image capture device operable to capture a plurality of video images; (ii) a storage medium by which said video images are stored for later retrieval; (iii) a feature extraction unit operable to derive image property data from said image content of at least one of said video images substantially in real time at said capture of said video images, said image property data being associated with respective images or groups of images; and (iv) a data path by which said camera-recorder apparatus is operable to transfer said derived image property data to an external data processing apparatus.