The video snaps demonstrate the utility of the dual focal length feature, where the foveal zone is the region inside the large circle. In the quad set of images starting from the upper right and proceeding CCW, notice how the man increases in size when he enters the circle and walks past the powerline pole in the foreground. He decreases in size when he exits again. Notice that the pole is perfectly straight inside the fovea and then decreases in width as it leaves the fovea. The change in width follows the gradual transition from distortion-free FtanΘ mapping to FΘ mapping. The purpose of FΘ mapping is to ensure that pixel sampling in the periphery remains constant with field angle, otherwise the edge of the field would oversample (and waste pixels) where it is not needed. The consequence is an appearance of barrel distortion, which can be corrected in software.