Explain how even though images appear on the retina in two-dimensional space, we are able to perceive objects in three-dimensions
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can someone answer this please? or give me an idea of this question? thanks
Possibly your answer is in the use of visual depth perception cues, both monocular (needing only one eye) and binocular cues (needing both eyes).
Monocular cues include relative size, interposition or overlap, linear perspective, shadowing, and relative motion or motion parallax.
Here is an article about binocular cues.
6/21/01
Visual Depth Cues: Near or Far?
David A. Gershaw, Ph.D.
In another article, we covered some of the monocular cues that allow us to see depth while only using one eye. Now we will discuss binocular depth cues – those that require two eyes. How do they work? How are they better than monocular cues?
In contrast to a multitude of monocular cues, there are only two binocular cues – convergence and retinal disparity.
If you are looking at an object over 50 feet away, both eyes are parallel. However – as the object gets closer than 50 feet, you eyeballs will rotate to come together. This is convergence. This movement allows the image from the object to fall on corresponding parts of each eye, so you brain can perceive a single object rather than two. If there is something wrong with the external eye muscles, so they do not converge well, this is one cause of double vision. (This problem can often be corrected by surgery.)
The stretching and puling of the external eye muscles send impulses to the brain to give you this depth cue. Some might respond, "I don't feel any pulling of my eye muscles!" Even though you may not be consciously aware of it, the convergence is still registered by your brain. To become aware of convergence, hold your thumb at arm's length in front of you. While watching your thumb, slowly bring it toward your face, unitl you touch the tip of your nose. Do you feel the eye muscles stretching now?
More people are aware of the other binocular cue – retinal disparity – because of its use in "3-D" movies. We have two eyes, approximately 2.5 inches apart. Because of this separation, there is a difference (disparity) between the images that fall on the back (retina) of each eye. The closer the object is, the greater the disparity of the images is on the retinas.
For "3-D" movies, two cameras are used. Their lenses are 2.5 inches apart, just like your eyes. You need to wear 3-D glasses to see these movies. These glasses allow only one image to reach each eye, reproducing retinal disparity. You perceive depth with monocular cues in regular movies. However, with "3-D" movies, the image seems to leap off the screen at you!
When we look at a regular movie or photograph, we can still tell that the screen or photo is flat. The same thing happens when we watch television. We can perceive depth, but the TV screen still looks flat. (Otherwise, we might try to reach in and grab some of the tempting foods that are shown on TV.)
Even though monocular cues help,
binocular cues increase the effectiveness of our depth perception.
How can the TV image have depth and seem to be flat at the same time? Essentially, it is due to a perceptual conflict between monocular and binocular cues. The monocular cues give the image depth, but the binocular cues indicate flatness. To illustrate this, find a photo that seems to have a great deal of depth. This means that the monocular cues indicate depth. However, your convergence will be the same for both near and far objects in the photo. Likewise, the same amount of retinal disparity exists for all objects in the photo.
To demonstrate the contrast between the photo and depth in reality, close one eye to get rid of your binocular cues. Now extend one arm fully, so your thumb covers a distant object. Now place your other thumb near the elbow of your extended arm, so your closer thumb covers both your other thumb and the distant object. Once you have done this, close the open eye and open the other one. Which thumb seems to move the most? Switch eyes repeatedly to experience the changes more fully. Because of the greater disparity, the closer thumb seems to move more. This should give you a greater appreciation of how your eyes combine images to give you retinal disparity.
To add more excitement to your TV viewing, eliminate you binocular cues, so only the monocular cues are used to experience depth. A good way to do this is to roll up a sheet of paper into a tube. Closing one eye, put the tube up to the other, so all you can see is the TV screen. The feeling of depth would be more apparent, if you are viewing a sequence that gives you the rider's view of going down a roller coaster, hang gliding or skiing down a slope. Since binocular cues are blocked out, your TV trip will seem more realistic. (However, I would not recommend this demonstration, if you have a weak stomach.)
So – even though you may still be able to get around adequately with only one eye, two eyes are better than one.
I hope this helps.
Well, well, well, looks like we've got ourselves a mind-boggler here. So, you wanna know how we can see things in 3D even though the images on our retinas are all flat and two-dimensional? Allow me, the magnificent Clown Bot, to unravel this mystery for you.
You see, our glorious brain is the mastermind behind this optical illusion. It takes the flat images received by our retinas and works its magic to give us the perception of depth and dimension. It's like a grand magician pulling a 3D rabbit out of a 2D hat.
There are a few sneaky tricks our brain employs to accomplish this marvel. One of the main tricks is called "binocular disparity," which is basically each eye receiving a slightly different image. These differences are then cleverly fused together by our brain, allowing it to calculate depth and distance.
Another trick up our brain's sleeve is the use of good ol' monocular cues. These cues include things like relative size, overlap, and perspective. They provide hints and clues to our brain about the three-dimensional nature of objects in our visual field.
And let's not forget about our good friend motion parallax. When we move our heads or eyes, objects that are closer to us appear to zip by faster compared to those at a distance. This helps our brain understand depth relationships and further adds to the 3D magic show.
So, my friend, it's all thanks to the incredible processing power of our brain that we can perceive the world in all its glorious three dimensions. Isn't it amazing how our brain can turn a flat image into a mind-blowing 3D extravaganza? Science truly is the greatest circus act of them all.
Certainly! I'd be happy to help explain how we are able to perceive objects in three dimensions, even though images appear on the retina in two-dimensional space.
Our eyes capture visual information through a process called vision. When we look at an object, light reflects off its surface and enters our eyes. The light first goes through the cornea, lens, and other structures of the eye, ultimately forming an image on the retina at the back of the eye.
The retina contains specialized cells called photoreceptors, which are responsible for detecting and processing light. These photoreceptors are of two types: rods and cones. Rods are sensitive to dim light and are primarily responsible for vision in low-light conditions, while cones are responsible for color vision and detailed visual perception.
Now, although the images formed on the retina are two-dimensional, our brain interprets this information and constructs a three-dimensional perception of the world. This perceptual process involves several visual cues that help us perceive depth and three-dimensional space:
1. Binocular cues: These cues rely on the input from both eyes and help us perceive depth. The disparity between the two retinal images, called binocular disparity, provides information for the brain to compute depth and distance.
2. Monocular cues: These cues can be perceived using one eye alone. They provide depth information based on various visual cues, including:
- Perspective: Objects that are farther away appear smaller, and lines that converge at a distance suggest depth.
- Overlapping: When one object partially blocks another, we perceive it as being closer.
- Shadows: The position and shape of shadows provide information about the relative depth and location of objects.
- Texture gradient: The level of detail and clarity of textures on objects can provide information about depth and distance.
- Motion parallax: As we move, objects that are closer appear to move faster than objects that are further away. This relative motion provides depth information.
These cues, both binocular and monocular, work together to create a perception of three-dimensional space based on the two-dimensional images captured on the retina. The brain combines these cues with previous knowledge and experiences to construct a rich and immersive three-dimensional perceptual experience.
In summary, our ability to perceive objects in three dimensions despite the images appearing on the retina in two-dimensional space is a result of the brain's processing of visual cues, including binocular and monocular cues, to interpret depth and distance information.
Of course! I'd be happy to explain. When images are projected onto the retina of our eyes, they are indeed in two-dimensional space. However, our perception of the world around us is not limited to just two dimensions. Our brain processes these two-dimensional images in a way that allows us to perceive the depth and three-dimensional aspects of objects.
There are a few key factors that contribute to our ability to perceive objects in three dimensions:
1. Binocular Vision: Our eyes are positioned slightly apart, and this allows us to have binocular vision. Each eye sees a slightly different view of the world. Our brain combines these two slightly different images to create a single, three-dimensional perception. This process is known as binocular disparity.
2. Depth Cues: Our brains rely on various depth cues to help perceive the three-dimensional world. These cues can be categorized as either monocular or binocular cues. Monocular cues include perspective, size, texture, shading, and motion parallax. Binocular cues, such as binocular disparity, provide depth information based on the difference between the images each eye receives.
3. Prior Knowledge and Experience: Our past experiences and knowledge of the world also play a significant role. Our brain uses this stored information to interpret the two-dimensional images and make assumptions about the three-dimensional shapes and structures of objects.
So, while the images projected onto our retinas are two-dimensional, our perception of the world becomes three-dimensional due to the complex processing and interpretation performed by our brain, taking into account binocular vision, depth cues, and prior knowledge.