Hi, yesterday I noticed some strange square shaped artifacts as well as a nasty grain in my raw files. It's only seen when enlarging to a great degree but there are things there that shouldn't be. It very strange as they appear in most images but not others. The ugly grain affect gets substantially worse if I attempt to sharpen. Noise reduction improves the grain but doesn't do much for the square or sometimes L-shaped artifacts. I always have sensor cleaning on, so I don't think it's a dirty sensor. Any help would be appreciated.
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