File:Motion-Extrapolation-in-the-Central-Fovea-pone.0033651.s001.ogv

English: Requirements and what to see: The demo video requires an additional blue filter with peak wavelength around 450 nm (e.g. the LEE filter – Tokyo blue). Please wear the color filter glasses and fixate on the center fixation point. In the first part of the movie, a dot moves continuously leftward and rightward crossing the fixation point. Viewing through the blue filter, you may see that the moving dot approaches and vanishes near the fixation point, and reappears further away from the opposite side of the fixation. The invisible gap between the reappearing position and the fixation, which you may perceive, is larger than the gap between the vanishing position and the fixation point. Without the filter or with green filter glasses, you may see continuous movement, or the moving dot approaches to the fixation point and a small gap after the moving dot crossing the fixation point (known as Fröhlich effect). In the second part of the movie, a bright disk flashes at 1 Hz. Viewing through the blue filter, you may perceive a dark irregular ‘ink’ spot (about one to two degree of visual angle, known as Maxell's spot) surrounding your fixated area. The irregular dark spot is due to the fact that yellow macular pigment absorbs the blue light and relatively low density distribution of short wavelength cones in central fovea.