Originally posted by Wired I'd say the jacket is the best place to bring the photo to 1:1 and see what I'm talking about.
Maybe I'm too pickey. I'm not a pixel peeper, but when I zoom in to do some post processing work (ie get rid of chromatic) it irritates me how noisy it is. Of course the image looks fine scaled down for web or printed even upto a 36" print
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I think that is the "issue" and "solution" of your question
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Any pictures in those conditions will give you a small, faint grain.
Even at ISO 100, on any camera you will have a very small faint of grain (especially when you zoom in) on unprocessed pictures - is normal.
However, for ISO 800 the amount of noise is so small I think is negligible.
It is slightly more visible on the jacket because of the light conditions (sort of back-lit) and the color of the jacket (or rather lack of it).
I would be more concerned on that CA that you are talking about