Some of my pics were rejected due to Grain/Noise issues. The issue seemed to be due to post processing as i shot in ISO100. Some of the pics in which i did post processing were accepted. In what cases the pictures are getting rejected due to noise..
You can go too far with sharpening. It causes a gritty effect, especially in non-detail areas. Try using the Mask in Camera Raw, and crank it up to cover everything you don't really need to be sharp.
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