VISUAL PERCEPTION of MOVEMENTS
Post 395 ⇒ by Gautam Shah →
We perceive objects that are in motion, and also perceive objects while we are moving. Motion of an object is perceived in many ways: 1 When there are changes in the object itself, 2 when environment causes changes, such as in illumination level, angle and colour, and 3 when the context such as background and foreground change. There are many other conditions where movement is perceived to have occurred, but in reality no change may have happened.
1. When there are changes in the object itself.
The process of apparent visual motion was realized when several pages with slight and progressive alterations were flapped, to experience the movement. Later a devices called zoetrope provided animated images ( zoetrope, -from Greek words, where zoe =life and tropos =turning). The Phenakistoscope (or phenakistiscope or phenakitiscope) was an image animation device that used a spinning disk of sequential images. The visual motion was also realized when two images shot at slightly distanced points, and seen through a ‘view master’ (1940). It created a stereoscopic 3-D image. A stereoscopic range finder uses two eyepieces and relies on the operator’s visual cortex to merge the two images into a single picture.
2. When the environment causes changes over an object.
Environmental factors such as light, air, etc. affect the visual perception of movements. Changes in illumination level, angle and colour are important aids for perception of motion. People do not perceive very slow movements such as shadows of sunlight or increasing-decreasing of brightness through a day. Such movements are however, inferred by remembering the previous condition. At a very high rate of change in illumination, the perception of an object becomes difficult. On a performance stage illumination level, angle and colour are continuously varied to reinforce the movement in dances. In a cinema the movement is enhanced by showing the moving object along with the moving shadows.
Decorative series of lights are stationary or fixed to buildings, but due to their going off in a sequence for few seconds, creates an impression of movement. This movement is more enhanced when same series of lighting are fixed on merry-go-rounds like entertainment rides. In Indian cinema songs, and night clubs at other places, enhance the dancers’ movement by strobe lights.
3. When the context such as background and foreground change one begins to perceive the change or movement. We register changes in things in some context. The context is provided by the familiar objects on the scene, by objects that remain consistent within the nominal field of vision, and by the object in the background that usually show lesser changes. A thing that is receding steadily and slowly, along a visual axial seems less changing, compared with a thing moving at slightly an angular axis. A luminous and stationary object, shrinking in size, seems receding.
Background and foreground perception is a not a major problem for human eyes, as these can continuously and rapidly shift from one to another. But the same process in a Camera takes time for resetting by manual or automatic process. A far object can become dulled while attending a foreground entity. The differences, of visual and camera perception of foreground and background objects, are being solved on several fronts. In one process a camera lens is simulated as multiple eyes entity, that individual captures the scene, which ultimately are merged or morphed to form a composite image. In another feature the lens is endowed with scanning capacity of the eye that creates a composite image.