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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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Which animals can see (or feel) the Moon’s infrared radiation?

The luminosity (bolometric) of the Moon in infrared is several times greater that its luminosity in visible light. Moreover, it may be rather possible for the Moon to be obscured by some fog or haze ...
Incnis Mrsi's user avatar
2 votes
0 answers
44 views

Eye Optics/Emmert's law: Where to place scaled copies of an object so they have identical images on the retina?

I read that the center of projection of the human eye is the entrance pupil. So given a light ray which intersects the objects position and the center of the aperture stop, all copies of said object ...
InteractiveCube's user avatar
3 votes
0 answers
37 views

Understanding David Chalmers claims on direct mappings between our vision and visual awareness systems

I am reading the popular 1995 paper "Facing Up to the Problem of Consciousness" by David Chalmers [PDF] as part of my philosophy course. I am only asking about the relevant vision related ...
Gaurang Tandon's user avatar
0 votes
1 answer
40 views

Term for a prey animal's recognition that something potentially threatening is looking at it?

On my daily walks I frequently see individual or small groups of cattle egrets. At first I would try to photograph them but they would fly away. This vexed me because they ignored everyone else ...
uhoh's user avatar
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1 answer
836 views

How much percent of image does our eyes focus at any instant?

I learned in highschool that even thought we have a wide view, we only observe a tiny fraction of that view through our eyes. So at any instant we are not really looking at all the objects infront of ...
gfdsal's user avatar
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2 votes
1 answer
150 views

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 ...
Ben's user avatar
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1 vote
0 answers
385 views

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 ...
James's user avatar
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1 vote
0 answers
249 views

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 ...
James's user avatar
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0 answers
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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?
Ritesh Singh's user avatar
1 vote
1 answer
319 views

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 ...
Somatic Custard's user avatar
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0 answers
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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 ...
MrX's user avatar
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2 votes
2 answers
167 views

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 ...
Rahul.In's user avatar
5 votes
1 answer
116 views

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 ...
James's user avatar
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3 votes
1 answer
98 views

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 ...
AP2261's user avatar
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6 votes
1 answer
790 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: ...
Bipasha's user avatar
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1 answer
164 views

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 ...
Evgenia Karunus's user avatar
1 vote
2 answers
145 views

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 ...
gapvision's user avatar
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2 votes
0 answers
190 views

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?
TheSmallestOne's user avatar
1 vote
1 answer
387 views

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. ...
Ruslan's user avatar
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2 votes
1 answer
1k views

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 ...
Positron12's user avatar
2 votes
1 answer
202 views

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?
Evgenia Karunus's user avatar
1 vote
0 answers
364 views

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 ...
Ruslan's user avatar
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5 votes
1 answer
78 views

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 ...
Harthag's user avatar
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0 votes
2 answers
2k 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 ...
gruszczy's user avatar
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2 votes
0 answers
50 views

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 ...
Sean Lake's user avatar
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3 votes
1 answer
90 views

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 ...
Sean's user avatar
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0 votes
0 answers
34 views

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 ...
Pandora's user avatar
5 votes
2 answers
482 views

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 ...
user234's user avatar
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2 votes
0 answers
27 views

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 ...
Sarra's user avatar
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0 votes
0 answers
39 views

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 ...
Ruslan's user avatar
  • 425
6 votes
2 answers
468 views

Can mammals and/or birds see / detect infra-red light?

Wondering if there is any evidence that mammals or birds eyes can detect light emitted in the infra-red? The reason I'm asking relates to the use of nest cameras to detect predators, using infra red ...
Damon Bridge's user avatar
1 vote
0 answers
50 views

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 ...
chompion's user avatar
2 votes
1 answer
485 views

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): ...
AzulShiva's user avatar
  • 123
4 votes
1 answer
3k views

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 ...
hasManyStupidQuestions's user avatar
31 votes
3 answers
9k views

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 ...
Daniel Mera's user avatar
0 votes
0 answers
61 views

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 ...
Combine's user avatar
  • 101
0 votes
1 answer
714 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 ...
Solidification's user avatar
0 votes
1 answer
2k 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?
user459284's user avatar
1 vote
1 answer
535 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 ...
Christopher Heckman's user avatar
0 votes
0 answers
40 views

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 ...
hello world's user avatar
5 votes
1 answer
152 views

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 (...
raisa_'s user avatar
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1 vote
0 answers
39 views

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?
Huma Qaseem's user avatar
2 votes
1 answer
1k 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 ...
Croad Langshan's user avatar
4 votes
1 answer
328 views

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 ...
Ruslan's user avatar
  • 425
2 votes
1 answer
246 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....
Ruslan's user avatar
  • 425
1 vote
0 answers
36 views

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 ...
creativecreatorormaybenot's user avatar
1 vote
1 answer
964 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 ...
Yesi's user avatar
  • 21
2 votes
2 answers
941 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, ...
Ruslan's user avatar
  • 425
3 votes
0 answers
120 views

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 ...
Fipah's user avatar
  • 59
30 votes
3 answers
10k views

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 ...
Timo's user avatar
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