Zhao, Dehua Xie, Dong Zhou, Hengjie Jiang, Hao An, Shuqing The influence of time of day on differences in digital number (DN) between vegetation and background pixels in vertical upward-oriented photographs. <p>From A to H, the photographic times were 05:00, 07:00, 09:00, 11:00, 13:00, 15:00, 17:00, and 19:00 h, respectively. A and H were taken before sunrise and after sundown, respectively, when there was no direct sunlight.</p> differences;vegetation;pixels;upward-oriented 2013-02-19
    https://plos.figshare.com/articles/figure/_The_influence_of_time_of_day_on_differences_in_digital_number_DN_between_vegetation_and_background_pixels_in_vertical_upward_oriented_photographs_/202056
10.1371/journal.pone.0051034.g004