Canon EOS 550D native ISO

The native ISO with the no or less noise are 160, 320, 640, 800, 1250, 1600, 2500. From 160 to 800 there is almost no noise at all and the 1250,1600, 2500 have an equal amount of noise. To able to enable these iso settings you need to install magic lantern on your camera.

View the test in the vid below which you can view the noise of different ISO, recommended to view it in HD will Full screen to able to see the tiny or large amount of noise.

Credit to Tim DaCosta for ISO test video view his Vimeo page here.