Questions tagged [vision]

Questions regarding how the brain interprets information from the eyes. Consider using the "eyes" tag for discussion of eye anatomy, physiology and evolution.

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Why does our visible range not include infrared or UV radiation? [duplicate]

As the radiation peak of the sun is in the UV region and since at around room temperature materials emit radiation at IR, I wonder why our eyes are not capable of using these wavelengths. I guess ...
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Why do we get tunnel vision during fight or flight response?

I have a question regarding tunnel vision during the fight or flight response. I believe that during fight or flight high levels of adrenaline are released which causes the pupils to dilate allowing ...
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Why do we have both on and off bipolar cells?

I have a question regarding the reason behind the 2 bipolar cells. So, from my understanding we have both on and off bipolar cells and from the numerous diagrams I have seen, I find that most show a ...
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Why does Cyan appear bluish rather than greenish, when the phototopic eye sensitivity is highest in green (and Cyan contains blue and green equally)?

Cyan contains blue and green equally. Phototopic eye sensitivity is highest in green. Why, then, does Cyan appear bluish to most of us, rather than greenish?
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Why do insects' “most sensitive photoreceptors” consume so much energy that it exerts evolutionary pressure to minimize their number?

The video Wireless Steerable Vision for Live Insects and Insect-scale Robots from the University of Washington's Paul G. Allen School of Computer Science begins with the following: Vision is an ...
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What is the smallest visual unit perceptible to the human eye, like a pixel? (esp. in visual static)

If you close your eyes, you can often see visual static, where individual pixel-like things are much more visible than with the more smooth, crisp images one gets with open eyes. This led me to wonder ...
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How does the human eye generate spikes?

Disclaimer: I have an academic background in computer vision but not biological vision. Background: Classical computer vision is concerned with images from cameras that have a fixed exposure time for ...
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2answers
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Is Brain Eye connections reversed in all animals or just Humans?

I know that Brain Eye connections are reversed in Humans, Left Hemisphere controls the Right eye/Right side of the body Right Hemisphere Controls the Left eye/Left side of the body Is it true in ...
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Vitamin A Deficiency

I have a quick question regarding Vitamin A deficiency. The photoreceptor molecules in both rods and cones have the same general structure which is retinal which is bound to a protein called opsin ...
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Visual receptive fields

What I know about centre-surround type receptive fields is that depending on whether the region is on or off, the response to being stimulated is either excitatory or inhibitory respectively. So if a ...
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115 views

Why did we lose our fourth type of cone cell (in the eye)?

Most species of birds, reptiles and fish have four types of cone cells in their retina, thus they have four independent channels for conveying color information. They are: short-wave (S) cones: ...
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Do L cone cells have a secondary peak?

I found some pictures on the internet suggesting that L cone cells (an in some M type too) have a secondary peak in the blue part of the spectrum. Is that so? Why would that be? (As if there is not ...
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Does opponent process happen in the retina or in the brain?

I understand that both the Trichromatic Process and the Opponent Process take place in human vision. Trichromatic Process is widely accepted to happen in the retina, however I heard differing accounts ...
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How do big cats perceive objects, specifically vehicles?

Right so we have been on safari in South Africa recently and before encountering big cats (lions) we have been told to hold still and not reach out beyond the boundaries of our safari vehicle because ...
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Does the human eye see things at twice the distance in a mirror?

If I'm standing 3ft away from a mirror and looking at something in it that is behind me but 5ft away from the mirror, do my eyes see that object as 3ft? Or 8?
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Why are eyes more sensitive to flicker in periphery — contradictory answers

In terms of the perception of flickering by CRT monitors, This answer suggests that peripheral vision has faster response and is thus more sensitive to flicker due to being provided by rod cells. ...
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How are the images of both eyes combined to form one image?

When you see an object by one eye, ex.right eye, you see it from the right direction and the opposite if you see it by your left eye, but when you open both eyes, the image appears somehow centric in ...
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1answer
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Vision: what is the difference between on-off ganglion cells and lateral inhibition?

Is 'lateral inhibition' just a term for the biological basis of the functioning of the on-center (or off-center) ganglion cells? Or do these terms describe separate processes?
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Is it possible to simulate tetrachromatic vision in a trichromat?

Suppose we are able to stimulate the whole matrix of cones of a human retina, targeting each cone individually¹. Normally we would project an image in the LMS color space onto the cones, in such a way ...
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Predatory animal tracking methods

As far as I know, humans are the only animals that use visual references to track prey that is not immediately visible to them. Do any other animals do this? I'm not referring to stalking prey ...
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467 views

How far can a human see at night?

I am not talking about seeing in total darkness, which I understand is not possible. I am looking more about a question how far can a human see during starry night or with half moon/full moon. I tried ...
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Do pale skinned people show other low light adaptations?

So, pale skin is, fundamentally, an adaptation to living in low light conditions. Pros: reduce energy spent on producing melanin, increase vitamin D production. Cons: more vulnerable to sunburns and ...
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1answer
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Comparion between machine vision & human vision

I hope this is the correct Stackexchange to ask this question. I am trying to know : What is the current status of knowledge regarding human vision and pattern recognition. More specifically, How ...
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Farsightedness and the eye

When a farsighted person looks at a distant object and sees it clearly, what is the state of their eye lens? Is it relaxed? Rationale: It is something we read about in class that is confusing.I know ...
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Understanding the “Waterfall Illusion”

Motion after-effect illusions, such as the waterfall illusion, refer to illusions where fixating a screen which shows stimuli moving in a particular direction elicits the perception of motion in the ...
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Is there benefit of use of red light over dim white light when interacting with rodents in the dark phase?

I've come across some "percieved wisdom" that rats and mice do not "see" red visible light and so use of this wavelength will allow humans to interact with rats in their active nocturnal phase without ...
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Are MacAdam ellipses theoretically predictable?

MacAdam ellipses were found as a fit to experimental results on color matching by human observers. Multiple color spaces attempting to make euclidean distances more perceptually uniform, like CIELAB ...
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What trajectory do action potentials take, from initial visual stimulus all the way to motor function?

Say we see a mosquito, and our brain tells us 'hey that's a mosquito, you should kill it.' Then we move our hands and slap/clap it. The initial visual stimulus is translated to an action potential ...
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What is violet color?

We have 3 color receptors in our eye, so assuming the above picture is precise we are checking for 3 wavelengths: 450nm, 540nm and 700nm. Pink for example has an RGB value of R (700nm): 1 G (540nm): ...
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Can crows see in ultraviolet? If so, does their plumage look different in UV?

Apparently birds which appear identical to the human eye can look quite distinct under UV light. Additionally, drab looking birds might have more "spectacular" looking plumage when considering ...
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3answers
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Can humans ever directly see a few photons at a time? Can a human see a single photon?

I am not asking the following question: Can humans ever see a photon in the same way we see a chair? My question is: Can a human retina respond to a single photon? If so, how does this happen and why ...
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Can creatures that can see color in completely different visible spectrum exists?

From wikipedia - "The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye." So humans can see the light from 400-700 nm and this is because our eyes can ...
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1answer
60 views

Why has the human eye evolved to become sensitive only to the visible light? [duplicate]

The human eye has evolved to become sensitive only to visible part of the electromagnetic spectrum. Why? Why is infrared vision disfavoured for us by evolution but not for some other animals? I am not ...
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What is the average eye sight for humans? How bad is one's eyesight if you are1 or 2 SD below average?

What is the average eye sight for humans? How bad is one's eyesight if you are 1, 2 or 3 SD below average? I googled but it was hard to find good search terms.
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278 views

While in motion, why do closer objects appear to move faster?

When I look outside the window while travelling by a car, why do closer things seem to be moving faster and appear unclear but the farther ones seem to be moving slower and appear clear?
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1answer
201 views

Multiple numbers in the Ishihara test?

When I was in high school (30 years ago), I took a biology class, and the instructor showed us an Ishihara color test for color-blindness. (This is the "hidden numbers" test.) What I thought I saw ...
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Does cataract condition cause red film when sun is shining?

Since two years ago I have a red film in my field of vision when the sunlight (or a white spot) is at the border (or even lightly behind) of the vision field, the red color is especially obvious at ...
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Do Colorblind People Have Stronger Sensitivity in Their Other Remaining Cones?

I came across this paper Color defect and color theory. The paper explained about how unilateral color blind (people who color blind only in 1 eye) actually see less bright in their color-blind eye (...
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Why green light is good for our health? [closed]

I have a knowledge that when you woke up and see green light it increases your sight power. How it does so?
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1answer
98 views

Can some colours be processed faster/more accurately than others?

Is the human visual / motor system able to track, and move in response to, objects of certain colours more quickly and reliably than for others? By more reliably, I mean with greater accuracy in ...
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Why is peripheral vision not bleached by daylight?

In daylight, rods are known to be bleached: we have to wait some time after going into darkness before scotopic vision becomes effective. But, as I understand, peripheral vision is also mostly due to ...
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1answer
204 views

How credible is the Remenko's two-component color vision theory?

I've come across an article (in Russian), which describes a nonlinear two-component color vision theory made in 1975 by S. Remenko. The article heavily criticizes trichromatic theory as very imperfect....
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Would preserving your Eyes from Light keep them healhty?

I read about why eyesight diminishes with age. I am aware of the fact that there are different causes that can affect the quality of image received by our eyes and that being vague would not lead to a ...
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1answer
483 views

Why do we fall asleep when our eyes are closed?

Why do we fall asleep when our eyes are closed? When we lie down with our eyes closed, eventually we'll fall asleep. Why is that? Is our eyes closing some sort of trigger to our brain that says it's ...
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345 views

Why is 450 nm monochromatic light perceived as blue or violet depending on its intensity?

Trying to do some color matching I purchased a 450 nm laser. I expected monochromatic light of this laser to have similar properties to those of all others I've already played with — 808, 640, 520, ...
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Can low melatonin levels and/or LED lights cause or exacerbate macular degeneration?

I have two questions that may or may not be interconnected. My first question is: Does melatonin prevent macular degeneration? Could low melatonin levels (caused by blue-rich light exposure in the ...
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Can one see flickering of a light bulb at 50 Hz?

Yesterday I had a BBQ with some friends. The sun had already set and the only light source left (besides some ambient light from the world around) was a low energy light bulb. After a while I started ...
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108 views

How do our eyes see an inverted image? [duplicate]

How exactly do our eyes see an inverted image of what we are looking at? Does it have something to do with the shape of our lens (i.e. convex)?
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How do you check how many cones you have in your eye?

Following my previous question: What color does the other cone in Tetrachromacy correspond to? People with normal color vision posses 3 cones in their eye. But there are some rare cases when people ...
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Melatonin production, sleep, and “cyan light”; how might this finding be possible?

The BBC News article Cyan colour hidden ingredient in sleep describes research that suggests melatonin levels as measured in saliva could be affected by the presence or absence of cyan color in a ...

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