My Canon has ISO settings of 50, 100, 200, 400. I generally stick with 100 and for some reason I haven't spent much time trying 50 although I probably should for landscapes. 200 and 400 are way too noisy to do anything more than record an instant in time. You can not get good photographs in any conditions at 400. The noise is bad. I sometimes have to use 400 indoors to capture moving people and it's almost not worth it. Even outdoors, such as when photographing my children in sporting events, I still get a lot of noise at 400.

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The only way of finding the limits of the possible is by going beyond them into the impossible.

Arthur C. Clarke

The Brain Science Podcast