We have two important shoots on the horizon and our tutor wants us to know our cameras strengths and weaknesses so we are competent when shooting. When you know the limit of your camera's ISO performance, you know what speeds to keep between when shooting in the field. This test from ISO 400 to 204,800 tells me how far I can push the camera.
When looking at the images on the computer I noticed how clean the files were at high ISO's, I realised when shooting in JPEG the camera can control noise much more effectively.
Up until ISO 204,800 the camera controls the colour casting pretty well. But at 204,800 there are large amounts of noise, colour defects and detail loss. (although the file size is much larger)