There are clouds passing overhead, out of sight that are affecting light levels. The camera is was in Shutter priority "S" and maintained an exposure time of either 1/640 or 1/800th sec to allow me to cope with the gale force winds. The exposure was adjusted by the camera accordingly, within the range of f/5.6 - f/8 but for the most part at either f/6.3 or f/7.1 (these are 1/3 stop increments if they don't seem familiar to some). Hence the change in the light levels. Hope that helps, John...