I know for a fact that the Nikon D610 is very clean up to 6400, and useable much higher... and that's a "prosumer" model, not by any means top-of-theline. It's just outrageous the amount of information that modern digital sensors are able to glean from what are essentially stray photons. I mostly use my old D5000 on nights like tonight, when "good enough" quality will suffice, and I'll be leaving it by itself at times. It's definitely noisier, but one can generally compensate for mediocre cameras with a fast enough lens.