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What Is Binocular Disparity? – Explained Definition and Important Factors to know about Binocular Disparity

For every binocular user, it is essential to have a precise idea of binocular disparity. In fact, it is not only vital for the binocular users, but it also is important for everyone who has expensive hobbies like hunting, birdwatching, camping, hiking, stargazing – meaning all those activities where binoculars play a significant role. Today we’ll talk about ‘What Is Binocular Disparity‘.

If you make a search on the internet using search engines like Google or Bing, you will find out lots of research papers are available out there focusing on this particular subject matter. But, for an ordinary person, it can be quite challenging to get a proper idea about binocular disparity by studying those research papers full of hard-to-utter terms.

Therefore, for the convenience of my readers, I made up my mind to make a thorough research of those papers and come with an easy-to-read discussion so that you can get to know about what binocular disparity is without any difficulty.

And, here, I have come with this piece of an article where I will talk about binocular disparity along with some other vital terms related to the subject matter.

Let’s get into the details….

What is Binocular Disparity? 

The term binocular disparity is referred to the difference in an object’s image location viewed by the right and left eyes, which mainly results from the horizontal separation (parallax) of the eyes.

The human brains use binocular disparity for extracting in-depth information from the world of two-dimensional retinal images through stereopsis.

In the case of computer vision, binocular disparity means the difference in the coordinates of similar or parallel features coming from 2 stereo images.

Joseph S Lappin, a researcher of Vanderbilt University, has done a great job through his research in the field of Frontiers in Psychology published on ResearchGate.

Important Factors You Need To Know About Binocular Disparity

In this section, I am going to give a brief idea of some factors that I think is important for everyone who wants to get a precise idea about the binocular disparity.

So, here we go….

Depth Perception

Depth perception refers to the visual ability of a person for perceiving the world in front of his eyes in three dimensions (3D) along with the distance of a particular object. For animals, the corresponding term used is known as Depth sensation.


Since our eyes are placed having a distance of 5-6 cm in between them, so the images projecting on each of the retinae are different to some extent. The difference in between those images is a cue to a depth which is known as binocular disparity.

Stereovision can be used or modified for creating three-dimensionality illusions, such as the glasses made for watching three-dimensional films. In order to demonstrate this, Bela Julesz did hard work for inventing dot stereograms in the 1960s which will always be remembered in history.

Binocular Visual Cues

As I have already mentioned, human eyes are 5-6 centimeters apart for which images seen on each retina are not exact in nature. And, this situation is called binocular disparity.

The two eyes when work together provides some kind of additional spatial cues. And, they are mainly classified or categorized as binocular cues. Among various types of binocular cues, the most prominent one is stereopsis.

Stereopsis, in the simplest term, is the compelling depth sense that mainly arises from the combination of the two eyes’ viewed images differences. If you close one eye suddenly (while seeing an object) then the other, you will experience a subtle shift in between those images viewed by each of your eyes.

Stereoscopic Vision

The term stereoscopic vision refers to the ability of your visual brain for registering a sense of 3D (three-dimensional) shape that forms from the visual inputs. In other words, stereoscopic vision can be referred to be to the sense of depth that is derived from your two eyes.

Static-Monocular Information

Though binocular depth cues can provide you with very accurate and exact information about depth, they are only functioning with a maximum viewing distance of 3 meters.

At the same time, around 10% of the total population doesn’t even have access to our subject matter (binocular disparity) because of the misalignment of the two eyes or maybe other problems related to the visual system.

Fortunately, there are other sources that humans can use for depth information, and kinematic cues, one of those sources, doesn’t rely on your two eyes.

Disparity Vergence

The radial pattern produced from the optical flow is only one of many cues that specify an observer’s forward motion. Horizontal binocular cue – another crucial cue – has also the ability to generate vergence eye movements.

In recent times, a study came up with the result that a sudden change in the horizontal binocular disparity of any large-sized scene can result in disparity vergence responses with ultrashort latencies of ~ 85 ms in humans and ~ 60 ms in monkeys (Busettini et al., 1994, 1996b).

Image Intensities and Visual Space 

The Venetian Blind Effect

Several phenomena are responsible for the reexamination of our current subject matter – binocular disparity. One of the primary motivations or reasons is the “Venetian blind effect (in short, VBE) – a situation where vertical gratings’ dichoptic intensity differences with the non-disparate edges can produce slight change, perceived change to be more accurate, in three-dimensional surface slant. Seemingly, the spatial disparity may not be necessary in this case.

Image Intensities and Spatial Positions

When it comes to monocular image structure, you have to keep in mind that it can involve spatial variations of intensity. Despite an observer’s representation of any physical dimensions, the intensity and space are not visually dependent.

The spatial position of any given optical features, such as edge, can easily be represented based on an independent reference frame, that can be related to the image structure’s surroundings. And, examples of both of the mentioned approaches are pretty much common in vision science.

Perceived Surface Slant is Imprecise

I must let you know the fact that perceived depth in the Venetian Blind Effect seems to be smaller, less reliable, and less compelling than that from the disparate spatial positions.

In reality, binocular vision seems to be a bit sensitive to the dichoptic contrast differences. For the contrast differences, there can be some effects on the perceived spatial positions for the case of binocularly fused images.

Binocular Disparity

In this section, I am going to tell you about what stereoscopic perception tells us regarding binocular disparity –

Disparity Involves Image Structure

In this case, the 1st principle that you need to know is that stereoscopic inputs involve the disparate image structures, not the disparate retinal positions. Besides, the stereoscopic hyper acuity is powerful under any random perturbations of each of your eye’s retinal image positions. Hence, monocular spatial positions can be best visually defined based on the surrounding image.

Disparity Involves Surface Shape

Another crucial thing you need to understand is that stereoscopic vision is directly sensitive to any environmental surfaces’ shapes. Also, the surface shape is differentiated more consistently than apparently simpler properties. And, the hyperacuity for the surface shape is controlled under some random perturbations.

Binocular Disparity in the Venetian Blind Effect

The VBE or Venetian Blind Effect mainly involves the perceived rotation of different vertical bars. Because of those planar rotations, you can experience some bilaterally symmetric dilation or, you may say, horizontal scale. In this case, the perceived rotation (mentioned earlier) seems to be an understandable and plausible result out of the image disparity.

Tricking Neurons with 2D Images

Brain cells or neurons, responsible for processing the visual imagery processed from the primary visual cortex (retinae) have the ability to detect the disparity existence through the inputs coming from the eyes. Precisely, these neurons will remain much more active in the specific part of the visual field to which they have the access to.

Frequently Asked Questions


So, having read the above informative discussion, I can draw the conclusion that you have got a clear idea of ‘what is binocular disparity‘.

From my end, I have tried heart and soul to make this discussion as simple as possible so that you can get a precise idea about the binocular disparity.

Now, it is time to hear your opinions regarding this article, specifically designed for you. So, don’t forget to comment below about your views.

Still, if you want to know anything more about the binocular disparity, don’t hesitate to message me.

I would surely help you out.

Take Care!

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