Motion parallax is a monocular depth cue arising from the relative velocities of objects moving across the retinae of a moving person. The term parallax refers to a change in position. Thus, motion parallax is a change in position caused by the movement of the viewer. Motion parallax arises from the motion of the observer in the environment. It is perhaps easier to think of what motion parallax is by imagining yourself as a passenger in a car looking out the side window. The car is moving very fast down the highway. The objects very close to the window, such as the small trees planted by the highway, seem to rush by. Beyond the small trees, you can see a distant farmhouse. The farmhouse appears to move more slowly relative to you in the car. You know that the trees and the farmhouse are standing still; you are the object that is moving. You can observe this phenomenon in the video below. This video shows clouds moving by a plane. The closer the cloud to the plane, the faster it appears to move. Show In this activity, you can see how motion parallax arises. Object that are farther away move move slowly across the retina as we move by them. Use this activity to observe how this gemometric relationship leads to motion parallax.
To see the illustration in full screen, which is recommended, press the Full Screen button, which appears at the top of the page. Illustration TabSettingsBelow is a list of the ways that you can alter the illustration. The settings include the following: Animate: Moves they eye from the top of the screen to the bottom, and repeats. This creates the motion necessary to show how motion parallax occurs. ResetPressing this button restores the settings to their default values.
An eye-catching science project from Science Buddies
Key concepts The human eye Peripheral vision Central vision Introduction Background The differences between central and peripheral vision start at the backs of our eyes where we have two types of light-sensitive cells, called cones and rods. Our central vision uses an area densely packed with cones. Cones are sensitive to color and need ample light to function well. Our peripheral vision uses mostly rods and almost no cones. Rods are sensitive to movement and quickly pick up changes in brightness. They function well in a broad range of light conditions. The differences continue as signals travel to the brain. Some signaling cells are sensitive to color but not so much to contrast whereas other cells signal faster and respond to low-contrast stimuli. In the brain’s vision center (known as the visual cortex) more neurons will analyze a stimulus picked up by our central vision compared with the same stimulus picked up by our peripheral vision. All of this leads to our color-sensitive, high-resolution central vision and our fast-working, movement-sensitive peripheral vision. With all this information on our visual system, will you be able to predict what your side vision will perceive? Try this activity to find out! Materials
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Observations and results Our peripheral vision is quick at detecting that something enters our field of sight but it is weak at distinguishing color, shape or detail. This is because fewer and different cells in our eyes and brains are activated when seeing an object with our peripheral vision than when “seeing” the object with our central vision. Our peripheral vision has evolved to serve us well. It is very good at picking up objects and movement in dim as well as bright light, which allows us to escape from an approaching danger quickly. This explains the results of some of the extra instructions: in dim light you still can quickly detect an object with your peripheral vision, and you notice it even faster when the object wiggles. Our ancestors did not need details to identify the type of danger instantly. To see color, shape and details, they could wait until ample light was available and use their central vision to study a relatively still object. More to explore This activity brought to you in partnership with Science Buddies Discover world-changing science. Explore our digital archive back to 1845, including articles by more than 150 Nobel Prize winners. Subscribe Now! |