Take a cardboard tube, such as from a kitchen paper role, and hold it close to your eye, while keeping the other eye open. Look at a bright wall. The disk-shaped area seen through the tube will appear strikingly brighter than the same surface area viewed by the other eye. The effect is reminiscent of a flashlight illuminating the area under consideration. The effect takes a few seconds to fully develop. It also works with a textured surface where it enhances not only the brightness and color, but also the detail.
