Hi. I have recently noticed a soft bright spot at the center of my images. It does not appear to be dust- which is present also! It is more evident in skies and is a noticeable bright spot. It cant be dust as the visible dust becomes sharper with small apertures and this doesn't. It is right in the center. I have not cleaned the sensor but have looked and there doesn't appear to be anything there. I am reluctant to clean the sensor in case this affects my warranty as the camera is only about 6 month old. Has anyone any idea what this might be. I am concerned it might be a defective sensor. Thanks I would add that it is evident when the lens is changed as well.