“Variance” images derived from videos of beaches studied

“Variance” images derived from the same videos used in the studies. Left, Madeira Beach; right, Cowells Beach. In a variance image, the more variation in light intensity at a given pixel, the brighter the value assigned to that pixel. Bright areas indicate many changes in light intensity, caused by a lot of movement. Note the bright zones of breaking waves and bright spots where people were shifting position on the beaches. In the Cowells Beach image, note faint light lines on far right caused by cars moving along West Cliff Drive.