Using Parallax in the Outfield
Parallax, specifically motion parallax, is a visual phenomenon that is relevant to baseball, particularly when catching a pop fly. Motion parallax is all about how objects at different distances seem to move at various speeds as your perspective changes. This effect is obvious in when tracking a moving object, like a baseball in flight, or a car in motion.
Good Catch Example:
Here we can see a baseball has been hit over the outfielder’s head.
The outfielder has taken an efficient first step and has created another perspective on the trajectory of the baseball.
The outfielder can see the ball is travelling quickly and is able to get in position to make the catch.
This phenomenon is why its so important to move efficiently to get the visual information needed to make a play on the ball.
No Catch Example:
Here we can see a baseball has been hit over the outfielder’s head.
The outfielder has taken a bad first step and has only one perspective on the baseball.
The outfielder misjudges the speed of the baseball and misses the catch.
Further Explanation
When you’re trying to catch a baseball that’s been hit towards you, your brain uses a mix of visual cues to gauge the ball’s position and trajectory. As you move or adjust your viewpoint to line up with the ball’s path, objects that are closer, appear to move faster than those that are farther away.
This movement offers important depth cues. In the case of catching a baseball, it helps you estimate the distance between you and the ball. By analyzing how the baseball’s movement contrasts with the fixed background, you can assess its trajectory and make informed decisions about when and where to intercept it.
By observing the motion parallax effect, you can infer the direction, speed, and even the curve of the ball’s flight path, all by comparing its motion with stationary objects in your visual field. All this happens in microseconds without conscious thought. You essentially synchronize your actions with the ball’s predicted path based on the cues provided by motion parallax.
There is an interesting clue in the definition of parallax. It is defined as: the apparent displacement or the difference in apparent direction of an object as seen from two different points not on a straight line with the object.
The “not on a straight line with the object” part presents an example I’m sure every outfielder is familiar with. The hard hit ball right at you that somehow files over your head. The best way to overcome this disatvantage by definition is by taking good drop steps to get off-line with the baseball, so we can then use the advantage of motion parallax to determine the ball’s trajectory.
Relevance to Depth Perception
Humans use a similar mechanism in order to perceive depth in our vision. We have two eyes in different positions in our head, presenting two views at the same time. This is the basis of stereopsis , which is the process we use to gain depth perception and estimate distances to objects.
Much like we have no ability to gauge depth if we have only one viewpoint, we have no ability to gauge distance and speed of the ball being hit if we stay in one place.
There is research that suggests they way we move is tightly integrated with the way we see.
Most of us percieve depth without ever having to think about it. There are tools like the brock string , that can train the mechanics of stereopsis and help people regain the ability to percieve depth.
Science Explanation
This phenomenon is also relavent to how we measure large distances that are too long for lasers to measure, like the distance of a planet from Earth. This can be accomplished by using two views to observe an object.
Using this principle of parallax, the distance can be measured by calculating the angle of observation from the two viewpoints.
Other Examples
There are many other applications that use parallax principals. Some of the more interesting ones are listed below.
- 3D photos from a single image
- wobble/wiggle 3D art
- optical and red dot sights
- Metrology
- Astronomy