为什么图片中上空会出现圆形物?请光学分析一下。
More information: it's not moon, no raining, no sound, I only notice it when download the photo in computer, therefore maybe only can seen by camera.
(I hope it's not ufo or sth unknown as myfriends think, cause if u enlarge the circle of this picture at certain point, you can see image of figure and cross sth, these photos were taken during my travel to other province ).