Questions tagged [vision]

Physical processes involved when seeing, and comparisons between with other light detection systems. Includes questions about the eye, optical nerve, brain, corrective lenses, etc.

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Would UV-induced-visible-fluorescence indicate the presence of vividly reflecting UV-invisible-light?

Some people take amazing photos by using UV-induced-visible-fluorescence(UVIVF). In my understanding, we see in these photos VISIBLE light induced by UV. https://www.nationalgeographic.com/photography/...
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3answers
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What is the pixel resolution of a human eye?

If it could be possible to build a camera inside a human brain that takes photos of what we see. What would be the resolution of those images in terms of pixel count? This question is not about ...
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1answer
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Why do 3D glasses only work from some distance?

I recently noticed that 3D glasses don't work if you are too close to the screen. Here is what I think what I know on how 3D glasses work: There are two images overlayed on the screen. Each of these ...
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1answer
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Do smaller organisms (eyes) see smaller objects in greater clarity?

Do smaller organisms (eyes) see smaller objects in greater clarity? With the human eye, as I get "closer" to something, I can see it in greater clarity, does this "relative largeness&...
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Why can't the human eye focus to make blurry photos/video clear?

The human eye focuses by flexing the lens, changing its focal length. When we switch from looking at a near object to a far object, our lens flexes, moving the focal length such that the near object ...
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2answers
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Why is the color of light not associated with frequency?

Imagine a green light source is at the center of a transparent material sphere and I am staying in the vacuum (or air) and looking to it. Now imagine that the wave length of the this light increases ...
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2answers
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Why don't we experience objects a little displaced from their actual positions when using eyeglasses as an effect of refraction?

We all know that as a result of refraction,when passing through a transparent/translucent object, the rays get slightly displaced from their actual path. So why don't people who wear eyeglasses ...
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Why is a simple magnifying glass placed very close to the eye?

My book answer is: There is only one convex lens in simple microscope which produces virtual,erect and magnified image when object distance is less than focal length.IN this case,real rays are ...
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How can focal length of the human eye lens change?

Shortsightedness is due to reduced focal length and long sightedness is due to increased focal length.howcan the focal length of eye lens change overtime?
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What makes a point on path of reflected light (while forming image) visible?

The path of light is not visible in vaccum,but only the source(reflecting surface) of light is visible to us. But in case of image formation, for example from a concave mirror, we see the image at ...
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5answers
178 views

Why does the brain interpret light from a mirror the way it does? [closed]

When we place an object above mirror and viewed from side, we see the image to be below the object, as if the reflected light is coming from inside the mirror. From the image above, the light from top ...
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2answers
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How we feel (perceive) exact size of object through our eyes?

Light after getting reflected from objects gets focused on retina by our lens. The images formed on retina is small, which is then sensed by our brain and depending on distance we feel size of that ...
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How photons make us locate the position of objects?

We detect an object with the help of light. When photons hit the retina our eyes find the presence of the source of the light (object), the source being the original source of detected light or ...
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1answer
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Why when looking at a laser's reflection the laser appears to have a ring of noise around the central beam?

When pointing my presentation laser at a semi glossy object like stained wood or my skin I see noise, almost like TV static (it also appears to be moving). Is this a property of the laser's refraction ...
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1answer
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Why do distant object look larger when viewed from an elevated position?

Can anyone explain the principle that results in a distant object being perceived as larger when viewed from an elevated position? eg: I notice when viewing a Shipping Vessel from the shoreline it ...
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1answer
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Is frame rate near the edge of the eye different than that in the center? [closed]

This is actually a biology question, but it has to do with frame rates, so I posted it here. Suppose, that you are looking at the lightbulb. Most of the lightbulbs nowadays run on alternating current, ...
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Why doesn't viewing blue sky hurt us like viewing blue light of digital screens?

It is said that all digital devices these days emit blue light rather than UV; long term exposure can hurt our eyes. Why doesn't viewing the blue sky for a long time hurt us? Is there any big ...
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How does Chromatic Dispersion affect your choice of 1.67 v. 1.74 high index lenses?

My dad must decide whether to buy 1.67 v. 1.74 Nikon lenses for his eyeglasses. Can someone please explain like I'm 5 this purported optometrist's comment on Reddit? This Webpage by Dr. Rüdiger ...
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Why we only see black colour when there is no light? [closed]

pls help me on it. I do not know if it is right but why do we only see black colour while there is no light.
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1answer
90 views

IR and UV transmissivity window of the (human) eye

Given this image: I just assume that the eye is made out of glass, so I wonder how is it that IR and UV radiation is absorbed by it? I would understand one of them but why is it transmissible for ...
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1answer
44 views

Focus at infinity

I have myopia so I wear corrective lenses. One set of glasses I have is designed to focus from about 2 feet to infinity. I can see the dashboard of a car, but I can also see buildings at long ...
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1answer
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Third Eye and how the brain would see the world [closed]

Let's suppose that through engineering, a third bionic eye would be attached to a human and interfaced directly with the brain. Let's assume this third eye is positioned in the middle of the forehead. ...
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How can we see objects with the help of light if we cannot see atoms?

We know that the objects are made up of atoms. We also know that we cannot see atoms with the help of light as the wavelength of light is too big in comparison to atom. So, my question is then: how ...
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How do we see things? [duplicate]

What I mean is, suppose white light falls on a red object and is reflected, so when we see the reflected light reaches our eyes we see it as red (probably because its wavelength corresponds to red). ...
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1answer
61 views

Why did a green light appear white when looked out of the corner of my eye? [closed]

The other day I saw a green light emitted from some source far away, and I realised that if I looked at it out of the corner of my eye I perceived it completely white. What is the explanation for this?...
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Why the color of light observed dark (almost no light) from section of overlapping of two different colored plastic sheets?

Two transparent plastic sheets say of red and blue color overlap as shown in figure . An observer looks at a clear sky through the sheets. He will observe light coming through sections as, SECTION 1: ...
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Why do we only see VIBGYOR colours from dispersion?

I read all the suggested duplicates and they seem to be addressing the relation between primary colours and VIBGYOR. But my straightforward question is when so many colours with different wavelengths ...
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1answer
112 views

How do we know that the peak of human eye sensitivity is at 555 nm? [closed]

How do we know that the human eye is most sensitive to a light of wavelength of $555$ $nm$ and power of $1/683$ watt? How are experiments performed for obtaining this result? What's so special about ...
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1answer
104 views

Why is desaturated orange = brown, but desaturated blue is just plain blue? [duplicate]

As per wikipedia, "brown" refers to long wavelength hues, yellow, orange, or red, in combination with low luminance or saturation. So what about the short wavelength hues? Is there any ...
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1answer
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Vision: eyes vs cameras

I think this is related to physics, and light waves. Is there some materials that can be seen by human eyes and can't be seen by cameras? (Imagine a special writing) Is that even possible therotically?...
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1answer
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If monochromatic light shines into our eyes, will that activate multiple types of cones or only one type of cone?

I have read this question: Explanation about black color, and hence color where John Rennie says: For example suppose you're looking at red light. Only the "red" cones will generate a signal and ...
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1answer
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How does nearsightedness know what's near versus far?

If I wear a VR headset, I still have to wear my glasses, because the image arriving on the surface of my eye is still arriving as if it were actually far away. But how does that work? Why does the ...
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11answers
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Are colors grounded in physics or are they a matter of human perception? [duplicate]

My father was colorblind, and I always wondered if colors were a matter of physics or if different colors are just a human way of describing and differentiating our visual perception of the world? ...
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1answer
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Which materials are white due to diffuse reflection, and which due to absorption/re-emission of all wavelengths?

Is there any way of knowing which white objects or materials are white due to emission of most or all wavelengths, and which due to diffuse reflection? If there is one type of material I would like ...
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10answers
6k views

What determines whether colors you can't see are visible or not?

So, when someone is red-green colorblind, the colors appear the same to them, like this: And if you're totally colorblind, then things presumably just appear like they would in a black-and-white ...
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1answer
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Can a person with healthy eye see things clearly if he/she uses spectacles?

Let's first see the mechanism of working of concave lens for correction of myopia. If a myopic eye has a near point less than infinity say 1 meter(m) then we use a concave lens of focal length 1, so ...
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Why do some kind of black bands or lines appear when I'm just about to touch two fingers ?There is a second question too [duplicate]

I don't know if I can explain this well. The effect is best visible when you keep your hand in front of a light source. When I'm almost about to touch any 2 fingers (assume between your thumb and ...
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Eye seen in sunglasses reflection

Today while laying down on the floor, enjoying morning sunlight I have noticed an interesting phenomenon. It is important to mention that I was wearing sunglasses - just regular, without any ...
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2answers
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What kind of information does light carry so that brain can “see” shapes and distances of objects? [duplicate]

I know that we actually see with our brain in a way that eyes only absorb the incident light upon them and they transform some sort of information to the brain and the actual "seeing" is done by the ...
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1answer
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If we had a good enough eyesight would we be able to see atoms and the fuzziness of the quantum world?

If our eyes had enough precision and calibration to see hundreds of thousands smaller scales than we do, surely our brains would also need a major tuneup to process it. But could our classical body ...
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1answer
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Why my myopia spectacles doesn't allow a person with normal eye to see clearly?

I am a student of class 10. I have been taught that myopia spectacles (concave lenses) corrects the vision by forming a virtual object at the person's far point. But I am unable to figure out one ...
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7answers
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Would visible light still be in a separate classification if we saw “colors” in a different wavelength? [duplicate]

Basically im asking if there's anything special about visible light other than the fact that we use it to see colors. If we saw in another wavelength, would it still be possible to see colors like we ...
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1answer
60 views

Astigmatism and focusing a camera

A thought experiment: assume I have poor eyesight, but using a viewfinder or an LCD screen I was able to focus a camera on an object or landscape with what seemed to me perfect clarity. I took the ...
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2answers
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Why is human eye dynamic range expressed in terms of luminance?

I am learning about photometry to do Physically Based Rendering. As I checked the human eye dynamic range, I was surprised to see it was expressed in terms of luminance ($\mathrm{cd}/\mathrm{m}^2$) : ...
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How can a contact lens on the eye's cornea produce a resolved image at the retina?

I'm going to take Wired.com's The Display of the Future Might Be in Your Contact Lens at face value and assume that the concept is legitimate (see also BBC and additional technical details in CNET). ...
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Human colour perception – summary needed

I am a graphic designer and I really want to have knowledge about human colour perception but the longer I am looking for and the more I read the harder this topic seems to be. Physics is not my ...
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Why don't we see the violet in the rainbow as blue?

I understand that we perceive the sky as blue and not violet because (1) sunlight has more blue than violet in it (see here), and (2) our eyes are more sensitive to blue than to violet. However, I ...
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2answers
49 views

How does human eye perceive distances? [duplicate]

In case of myopia a parallel beam of light appears to come from the far point of the eye when we use corrective concave lenses. But we do not perceive it as it is coming from the far point, instead we ...
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1answer
80 views

Why does the image lose its clarity when it is formed in front of the retina?

This idea is not intuitive to me. How can the formation of image in front of or behind the retina be not clear? Why does the converging point of the rays of light produces a sharp image? Is it ...
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Why is the maximum power of accomodation of human eye about 4 D?

I visited some websites and they state that it is because the least distance of distinct vision is $25\,\mathrm{cm}$. However, we know that the diameter of the eyeball is $2.3\,\mathrm{cm}$, so $v=2....

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