• Background
  • Instructions
  • Illustration
  • Quiz


Disparity arises because our two eyes are in different locations in our head and therefore have slightly different views of the world. If you hold your finger out at arm’s length and then look at it alternately with your left eye only and then your right eye only, the image of your finger relative to the world behind it will shift somewhat. This is binocular disparity, which helps provide the basis for the determination of depth.

The explanation of how disparity allows us to extract depth information is quite complex. So work through this and the next set of activities slowlty, make sure you understand the activities, and review them until you understand these concepts well. Only after you have done that can you be sure that you understand the explanation of stereopsis.

Use this activity to explore the basics of binocular disparity and how it is related to vergence.


Full Screen Mode

To see the illustration in full screen, which is recommended, press the Full Screen button, which appears at the top of the page.

Illustration Tab


Below is a list of the ways that you can alter the illustration. The settings include the following:

Disparity Object X Position: Moves the disparity object (the green dot that is not being 'looked at') closer or farther from the eyes.
Disparity Object Y Position: Moves the disparity object up and down on the screen.
You can also move the dot by clicking and dragging on the screen with a mouse or by touching the screen. Fixation Object Position: Moves the fixation object (the red dot that is being 'looked at') closer or farther from the eyes.
Eye Separation: Makes the eyes closer or farther apart. The farther the separation, the greater the vergence change and the more disparity.


Pressing this button restores the settings to their default values.