What could be the problem? Well some research has been done at the Beyond3d forums, suggesting that Ratchet and Clank is 704p or 704by1280 pixels instead of the regular 720by1280. This is unlike the Halo 3 problem of being a 640p image (or even Conan at 576p) being upscaled to 720p (and higher) since Ratchet and Clank is not upscaled by the Playstation3.
Upscaling from 640p to 720p would cause some strange exaggeration of aliasing, and other minor problems with picture quality. Instead, Ratchet and Clank cuts off 8pixels above and below, meaning the remaining image will still be rendered at 720p but with small black bars above and below, such as you would see when you watch an HD film on your television. A 1080p film will have black borders above and below, thus not using all the pixels, but the quality that is displayed still means it is 1080p. Ratchet and Clank is even less extreme than this, since the black borders would be almost unnoticeable if your HDTV didnt use overscan to remove them completely. This image is sent from the Playstation to your television, and then the overscan of your television will make the final picture fit the screen, thus not showing the black bars. Ratchet and Clank being 704p is thus a clever way to save some pixels without impacting visual quality
