Space shuttle today 5Dmk111 & 100-400

...why on earth shoot f/16???

Why not stop down to f/8.0 where the 100-400 is so sharp and then reduce your ISO significantly??? There's a ton of grain in this which is surprising since it's the MkIII, but you could have come out with a spectacular shot, rather than a decent capture of a rare event I wish I'd seen in person (stupid mid-town office with no window view...)

TIS
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