I see a strange artifact with my Hitachi TX100. It is hardly noticable and seen only when the image is completely black, so it does not bother me as such, but may be it is related to something that might get worse. When the image is black, I see 3 small circular areas (at what seems as random spots) which are a bit lighter than the rest of the image. These circles grow or reduce in size, when the iris is opened or closed. Does anyone have an idea what this is?