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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19 views

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
29 views

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
10 views

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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0answers
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What are eye recognition skills? [closed]

I wonder what should be diameters of two monochrome spots, to make them recognizable by human eye. I know the distance from spots to eye, wavelength, a pupil size.
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10answers
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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
43 views

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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32 views

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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2answers
81 views

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
56 views

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
38 views

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
47 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
64 views

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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2answers
53 views

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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1answer
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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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2answers
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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
47 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
51 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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1answer
238 views

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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1answer
88 views

Why do things look bigger when you're far away?

When I'm on my bed looking outside the window, the trees in the park which is quite some meters away looks big and closer than the actual distance. But when I get up from my bed and go and see it ...
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2answers
44 views

Observable detail and wavelength of light needed to observe - How they are connected?

"If we use light to look at the structure of an object, we need to have its wavelength smaller than the size of the details we wish to look at". I read this statement in an answer at Physics ...
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1answer
68 views

Spectral sensitivity of the human eye -

Following the question: Sensitivity of eye I would like to make sure what these % says about? Is it the ability to colour detection? The similar stuff is here: http://www.giangrandi.ch/optics/eye/...
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1answer
80 views

How does a yellow colour filter work in the sense of RGB colour model?

I learnt after reading How do color filters placed in front of a light source,change the color of light that passes through? colour filter work by permitting only one colour and absorbing or ...
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1answer
86 views

Quantum mechanical reasoning to seeing colours

I don't know if I am writing but this is how I understand it: If I am looking at blue paint... White light falls onto the paint, the electron in the atoms of the paint absorbs all white light and ...
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3answers
67 views

A single eye vision vs normal vision [closed]

I am trying to understand the basics of human vision and looking for a model to see pros and cons of a single eye vision vs two eyes vision. Generally my interest relates to a basic project in a ...
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3answers
71 views

Wouldn’t a truly yellow object appear black in a picture?

If I have a truly yellow object, one that reflects only the light with wavelength between 570-590 nm, and photograph it with a camera that detects only RGB to put it together as a color image, would ...
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0answers
28 views

Wavelength absorbed by cornea but not by air

I'm interested in mounting laser diodes on servos and using them to transmit data. However, I'd rather not accidentally blind someone, even if they (say) stare for five minutes into the beam. My ...
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4answers
111 views

Why do we see black objects if they absorb all frequencies?

Black object absorb all frequencies, yet maybe some light is reflected anyway, but why do we see pitch black?
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2answers
46 views

How can the sky be blue and transparent at the same time, from below and above?

The sky is blue, when looking from below. That's based on scattering, no problem with that: Why is the sky blue? But it is also colorless transparent from above. No problem with that either, we look ...
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1answer
32 views

Seeming darkness inside at dusk/dawn with lamps

My question is about a fairly common phenomenon related to light and vision. When you are inside a room with lamps inside that also has windows, your capacity to see well can depend on both the light ...
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3answers
369 views

Effect of layout on text visibility [closed]

My college recently switched to whiteboards. Though writing on a whiteboard with a black ink sounds similar to the conventional way of writing with white chalk on a blackboard, it feels very different....
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3answers
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Can you guess the approximate size in mm of Snellen/vision chart letter? [closed]

I searched a lot but nobody is telling the size of letters of 6x6 vision. Basically, I need to create a rough sketch of any letter of a 6x6 row in Snellen chart. Some sites say it is 8.7 mm from 6 ...
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1answer
27 views

What information can our eye-cones actually extract from a spectrum of illumination?

If I understand correctly, the cones in the human eye work as follows: the three types have a degree of sensitivity for each wavelength. A cone is activated in a one-dimensional "degree of activation",...
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0answers
33 views

Will myopic vision be improved while diving?

Why does my myopic vision improve under water while wearing a diving mask, compared to my normal vision on land?
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0answers
22 views

How large will my buddy's eyes appear underwater while wearing goggles?

My buddy and I are underwater scuba diving. We are both wearing diving masks. I know an object in the water will appear 1.33 times larger. But how large will my buddy's eyes appear inside of his ...
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0answers
42 views

Could this work as a way to make 2D appear 3D? [closed]

So there is an effect where if you close one eye while watching a 2D movie, it appears slightly more 3D. This being because your depth perception no longer has the cue from two eyes. (As an ...
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1answer
40 views

On seeing and especially in the dark

Our retina detects the change in the electromagnetic field due to the jiggling of the atoms surrounding us as I understand the seeing process. In the total absence of a light "source", however, why ...
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2answers
37 views

Is their a way to protect screens from being recorded? [closed]

This idea might sound stupid but... Is there a way a screen would be impossible to record using a prism? I’m not talking recorded by a software but recorded from a camera… If you put a prism layer in ...
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1answer
36 views

Vision bluriness

I don’t know much about vision so I hope one of you guys could clarify me… When people who have vision problems look at an object without their glasses, they’ll see this object with a certain level ...
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0answers
22 views

Reverse engineering visible color spectrum with night vision glasses

Here's the context from a discussion I was having with a friend. Let's say I have a picture on my phone. Would it be possible to watch this picture on my phone with night vision glasses who usually ...
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1answer
48 views

How does the eye see a real image?

If we look at a convex mirror diagram, it produces a real inverted image at the bottom. Let's say a person's eye is above the object. How do the reflected rays reach the eye? since it's a concave ...
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3answers
111 views

How do we see virtual images?

Here in the diagram rays coming from B' point falls on two different places on retina of eye.So we should see B' at two different places. But it doesn't happen like that in reality. Is my logic wrong? ...
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0answers
48 views

Estimating focal length using light

I am considering how to estimate the focal length of a dynamic lens (such as biological lenses) non-invasionally, i.e., without harming the animal. The mammal lens changes its shape depending on ...
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1answer
69 views

Astronauts in spacecraft, they have to circle the earth many times a day, do they also have the illusion of the moon?

Astronauts in spacecraft, they have to circle the earth many times a day, do they also have the illusion of the moon? I don't think they have, because according to the theory, the illusion of the moon ...
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0answers
35 views

Why can distant objects be focussed more clearly when they are illuminated more brightly?

On a bright summer day, I can look down a straight highway and easily make out signs and some details of typical roadway objects that are at least hundreds of meters away, perhaps a kilometer or more. ...
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48 views

How to explain this thumb experiment?

Close your thumb to your eyes and align your eyes, thumb and moon. Then focus your eyes on your thumb and watch the moon behind your thumb. You will find that the moon becomes small! Remove your thumb ...
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2answers
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Is it possible to, using electromagnetic radiation, see the skeleton through a hand with your eyes? [closed]

Using electromagnetic light in the spectrum that can be seen by photoreceptors in the human eye, is it possible to produce an image of the bones onto the human retina?
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29 views

Photometry - Photopic and Scotopic vision

I would like to measure the eye sensitivity to a blue LED when a person is placed in a dark room. I need to convert the luminous flux (lumen) to optical power (W). Can someone tell me if I should use ...
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1answer
54 views

How do I explain the below phenomenon I am seeing along the edges of my eyeglass lenses?

I am near-sighted. Here is the phenomenon: I stand in front of a light source that is situated on the ceiling so that it reflects off my eyeglass lenses and appears circular. It is a white light ...

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