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Richie Vallance

Depth Perception, 3D Vision, and Binocular Disparity in Shooting

When focusing on an object, your eyes converge inward until both are fixed on the same point. Because your eyes are positioned a few inches apart, they each capture slightly different images of the object. The brain combines these images into a single, three-dimensional (3D) view, giving us the ability to perceive depth and distance. This phenomenon is known as binocular vision, and the resulting image is referred to as a stereoscopic view.


Binocular disparity refers to the difference in the image location of an object seen by each eye due to the horizontal separation of the eyes (parallax). The brain uses this disparity to extract depth information from the two-dimensional retinal images, enabling us to triangulate an object’s position. 


The Impact of Binocular Disparity on Shooting

In shooting, binocular disparity can cause challenges when focusing on a target. For example, when a gun is raised into view while focusing on a distant object (the target), the gun appears in the foreground and can cause double vision. This occurs because the eyes remain fixated on the distant object, and anything in the foreground, such as the gun, is not seen stereoscopically.

This phenomenon explains why some shooters experience double vision of the gun when focusing on the target. It also debunks the common advice to “just focus on the target” when dealing with eye dominance issues—this oversimplified guidance does not address the underlying problem.


The Framing Test


The framing test is a simple way to evaluate the balance of binocular vision:

  1. Stand facing an object in the distance, such as a clay target or a spot on a wall.

  2. Extend your thumb in front of your nose, pointing at the distant object, and focus your eyes on the object.

  3. If both eyes are balanced, you will see two slightly blurred thumbs framing a focused image of the object.



 

Eyes focused on the target: The clay appears sharp, with two slightly blurred thumbs.

 









Eyes focused on the thumb: The thumb appears sharp, with two blurred clays framing it.

 





If you cannot see two thumbs or if one thumb appears faint or ghost-like, this could indicate imbalanced binocular vision or strong eye dominance. Shooters with strong dominance in one eye may see only one thumb, while those with central vision often see two thumbs equally blurred.


The Shooter’s Perspective: How Binocular Disparity Affects Aim

Shooters with varying levels of dominance perceive the target and gun differently. The images below show three scenarios which can be experienced by a shooter suffering binocular disparity (in this case shooting a crossing target). You will note that the shooter is staring at the target in all three scenarios and the clarity of the gun suffers once divided into two.


The next set of images explain what is happening in three different scenarios.


Right-Handed Shooter, Right-Eye Dominance (Image 1):


·      The dominant (right) eye aligns through the gun’s bead to the target.

·      Both eyes converge on the clay, creating a stereoscopic view of the target, while the non-dominant (left) eye contributes peripheral vision.

·      Binocular disparity causes the non-dominant eye to see the gun slightly offset, resulting in a faint double image of the bead. In strong dominance, the non-dominant image may disappear entirely.



Right-Handed Shooter with Central Vision (Image 2):


·      The gun aligns between the two eyes, and both eyes see it from slightly different angles.

·      The combined image shows two barrels or beads, one on either side of the target, which can confuse the shooter and disrupt aim.



 

The Context of Shooting with Both Eyes Open


While shooting with both eyes open has significant advantages—better peripheral vision and depth perception—it’s not suitable for everyone. Strong dominance in the master eye is a prerequisite for this approach.

Unfortunately, some advice given to shooters lacks nuance. For instance, the notion that “clay shooters should always keep both eyes open” is unhelpful without context. While elite shooters often shoot with both eyes open, this works because their dominance is naturally aligned with their handedness. Without addressing dominance issues, advising all shooters to shoot with both eyes open can cause more harm than good.

A personal anecdote illustrates this misunderstanding: During a conference, an elite shooter was asked, “Do you shoot with both eyes open?” Their simple answer, “Yes,” satisfied the audience but lacked the context of their natural dominance alignment. This illustrates the importance of individualised advice tailored to the shooter’s specific needs.


Key Takeaways


  • Binocular disparity is a natural phenomenon that can impact shooting accuracy.

  • Shooters must understand how their eyes perceive the gun and target to address issues like double vision or misalignment.

  • Solutions vary from simple physical adjustments to specialized tools, and there’s no “one-size-fits-all” remedy.

  • Coaches should focus on diagnosing dominance and disparity issues early to tailor corrections and improve performance.

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