Occasionally I will open a picture and the image will show rings of blotchiness or shading on large areas of the same color. It can be a face, a background, or both but it is always a somewhat regular circular or oblong pattern much like ripples in water or the grain pattern of some wood.
My question is what causes this? I never see it on this site or other photorgraphy websites so I am assuming it is either from over processing, low resolution pictures, or something I haven't thought of. I have tried to find an example to post but so far have been unable to find one. Anyone have an explanation?
