Excerpt: The S640 is attractive in terms of specification, fast 2.7 lens and high ISO6400 capability but the marketing and the experience do not match up. In good light it takes excellent photos. In poor light conditions set on high ISO it does Nikon's reputation no favours. Nikon can do better than this. Set it on fixed ISO range maximum 800 ASA and it works OK. 6400 images are so soft with high interpolation and complete loss of detail to the point of being nearly unusable.