Whenever Canon comes out with new cameras, one of my most important real-world tests is determining how clean the images look at higher ISOs. I am not testing this for scientific reasons, I am doing this test because I shoot in low light quite often and want the highest quality images for my clients. I also thought that you and the rest of the world might be interested in this as well.
Many people get caught up in the number of megapixels that a camera has on its sensor, thinking that the more the better. What people may not know is that the more megapixels they cram onto a sensor, and the closer that those pixels are to each other, the more heat build-up occurs. This increase in heat can ultimately also increase the digital noise (graininess) in our photos.