Never got this on my M8 although taking many pics in museums with some bad spotlights at times. However I know that theory says it may occur with CCD sensors (not with CMOS), if I recall it is a problem of saturation of electronic charges etc. and it will leave a horizontal dark band on the lines where the light is. I was warned against this by a friend physicist before I bought my M8 but did never get the effect, even with the sun in the field of view.