Binocular Cues vs Monocular Cues-Definition, Difference and Uses

Monocular cues provide depth information when viewing a scene with one eye while Binocular cues provide information taken when viewing a scene with both the eyes.

In this article, we learn about depth perception, What are Monocular cues and Binocular cues, the Difference between them and, how we can use them.

Let’s move onto learning depth perception first, which is important in learning about the cues;

Depth Perception

Depth perception deals with the ability to see the environment in three dimensions and estimate distances of objects from us and from each other.

It is critical for our survival, as it helps us to navigate effectively around and function in the world.

Without the perception of depth, it would be impossible for us to tell how far objects are from us, and how much we need to cover to reach them or avoid them.

Our ability to perceive depth includes space perception, or ability to perceive differential distances of objects in space.

Questions linger as to how we will be able to perceive the world in three-dimensions; when images projected on our retina are two-dimensional and flat?

While depth perception is a result of our visual sense, our hearing sense also plays a major role.

Depth perception can be perceived under two broad classes of cues namely monocular cues (using one eye), and binocular cues (using both eyes).

Motion Perception

Motion perception is the process of inferring with the direction and speed of elements in a scene based upon visual input.

Monocular cues, or what we see from one eye, can detect nearby motion; but depth perception isn’t up to the mark. As such, binocular cues are better at perceiving motion from distance.

There are 2 types of motion perception, namely first-order motion perception and second-order motion perception.

While first-order motion perception happens due to specialized neurons in the retina, that tracks motion through luminance, as per which an object needs to be directly in front of the retina.

Second-order motion perception occurs by examining changes in an objects’ position overtime via feature tracking on the retina. This helps detect motion by change in size, contrast, and texture.

What Are Cues

Cues or optical cues is the depth perception of the eye while viewing an object at a particular distance. Depth perception arises from a variety of depth cues that portray special capability.

A cue is nothing but visual cue; which implies the sensory cues received by the eye by way of light and giving a visual perception. As visual system is dominant in many species, especially humans.

Visual cues form a source of information for humans helping them decide how the surroundings are to be perceived or seen. It is here that monocular cues and binocular cues come into play.

In general, sense while monocular provides deeper information about a particular scene when viewed with one eye; whereas binocular cues provide in-depth information about a particular scene when viewed with both eyes.

It is this need to get the best or the clearest picture that weighs upon someone while going for binocular or monocular.

What are Monocular Cues

Monocular cues are essentially the cues that allow us to see depth using just one eye, or to detect how near or far an object is in relation to our position with one eye.

Monocular cues play an important role in detecting depth. It uses one eye and image can be presented in two dimensions.

As such, many of the monocular cues are used in art to create an illusion of depth in a two-dimensional space.

Monocular cues are actually a collection of cues that help us see an object properly using just one eye. These are as follows: –

1. Absolute Size, not knowing the size of an object is problematic for us, in such cases, the smaller object is considered at a greater distance than larger objects at the same location.

2. Motion Parallax, it describes the way stationary objects appear to be moving at different speeds against a background when we observe it moving.

3. Familiar Size, familiarity with the size of objects helps us determine how far away they are from us.

4. Texture Gradient, the amount of detail we can see easily on an object when it is close to us; when far we can’t see the detail.

5. Reach Trajectory, it shows direction bias during monocular viewing, especially in the approach phase. This bias is consistent with the presence of esophoria in monocular viewing. Esophoria is present when occluded eye deviates medially and exophoria is present when occluded eye shifts temporally.

6. Relative Size, size does matter; by knowing how big two objects are in relation to each other, how far away they are from each other and we can be figured.

7. Linear Perspective, parallel lines seem to converge at a distance; the farther they are, the closer they seem to us.

8. Natural Effects, like heat haze, water vapor, dust, sand, and fog, can affect our vision, especially at longer distances.

9. Interposition, when an object partially overlaps or obscures another object; it helps us to put the distances of objects in order of the nearest one first.

10. Aerial Perspective, objects at larger distances from us are affected by natural scattering of light and form less of a contrast with their background; making it harder to gauge a distance between the two and us.

11. Accommodation refers to the amount of work our eye muscles like ciliary muscles have to do to focus on an object.

12. Shading and Lighting, the nearer an object is to light, its surface appears to be brighter. In a group of objects, darker objects tend to appear farther away than the brighter objects.

13. Depth from Motion, as an object moves closer, its size increases in the eyes of an observer; this helps determine the pace of its movement and its distance from us.

Binocular Cues

Binocular cues are defined as the ability of both of our eyes to perceive an object in three-dimensional space. It’s much easier for our brains to accurately calculate the depth and distance of objects when we use both eyes.

These cues are based on different images that our two separate eyes produce. Binocular cues are a collection of cues that help us see an object properly using both eyes. These are as follows: –

1. Retinal Disparity also called binocular parallax, that refers to the fact that each of our eyes sees the world from a slightly different angle, which is triangulated by the brain to figure out the correct distance

2. Binocular Convergence refers to the amount of rotation our eyes have to do in order to focus on an object. It enables us to determine how near or far things are away from us. A proprioceptive sense, it is the amount of inward rotation our eyes have to do in order to focus on an object.

Advantage of Binocular Cues

1. Binocular cues allow us to take advantage of a spare eye. Even if one is lost or damaged there is still another one left.

2. it gives us the scope of a much wider field of view.

3. Retinal disparity and binocular convergence can be used to distinguish the variation in distance.

4. It allows us to partially see an object behind an obstacle.

5. It allows binocular summation that helps improve contrast sensitivity, brightness perception, visual acuity, and also flicker perception.

6. Binocular viewing can happen at different stages of information processing and can have a cumulative effect on an overall improvement in the performance of fine motor skills.

7. The binocular summation is one factor that results in faster reaction times when we are viewing something using both our eyes.

8. Binocular viewing also helps activate a more direct cortical path for planning, reaching and grasping of movements.

Conclusion: Monocular Cues Vs Binocular Cues

Monocular cues and Binocular cues are used in our everyday lives, even if we are unaware of it.

There is little existing data to proves beyond doubt as to how well, we humans are able to discriminate between distances under natural conditions.

Based on depth perception and motion perception, monocular cues regard results in a more illusory experience than binocular cues. The image we see from our right eye is always slightly different from our left eye, but the image we see with both eyes is a merger of what we see individually with both the eyes.

While binocular cues help us to expand in more than one perspective in the form of an object in order to get apt depth perception.

Monocular cue sensitivity, on the other hand, depends on the visual field location, which is relative to the stimulating.

Over the years, research has shown that binocular viewing actually provides’ a better advantage in complex environments, such as, when multiple objects are present, for example during bird watching.

Basing on the above-mentioned factors and keeping in mind your budget, you can go for a light-weight monocular or a heavier binocular.

Sources: Wikipedia

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