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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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29 views

Why do I see two of every object?

When I place one finger in front of my eyes and focus on something far, I see two fingers. When I focus back on finger I see the far things becomes two and finger becomes one.
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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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2answers
50 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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37 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 ...
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1answer
47 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 ...
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28 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 ...
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2answers
102 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 ...
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21 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 ...
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16 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 ...
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29 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 ...
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1answer
49 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): ...
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1answer
131 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 considering ...
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21 views

Information density of sight vs hearing

Is human sight more information dense than hearing? Is there a way to estimate the information density of these senses?
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3answers
8k 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 ...
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34 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 ...
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1answer
55 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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1answer
127 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
119 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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29 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 ...
5
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1answer
96 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 (...
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38 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?
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1answer
66 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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1answer
122 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 ...
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1answer
198 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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29 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 ...
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1answer
323 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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2answers
247 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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3answers
6k 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 ...
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1answer
89 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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1answer
306 views

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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2answers
233 views

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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1answer
48 views

What are reciprocal inhibitory synapses?

Quoting Kandel's Principles of Neural Science, 2013, Amacrine cells generally receive excitatory signals from bipolar cells at glutamatergic synapses. Some amacrine cells feed back directly to the ...
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43 views

Camera and the eye (filtering information)

How does a camera recreate a very similar perceptual stimulus (through the photo) for us to see compared to the person directly viewing the object of interest with their eye? My questions stems from ...
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31 views

Nocturnal Animals whose Eyes Don't Shine

Are there any classes of animals which are mostly nocturnal and rely on their eyesight to a non-negligible degree whose eyes still don't shine during the night? In other words, are there animals ...
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1answer
84 views

Best colour for a dog to track an object against green background

As dogs have limited colour perception, what colour would appear with most contrast against a green background for a dog? I understand that red and green are very close in a dog's colour perception, ...
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0answers
28 views

How many colors can colorblind people really see compared to normal color vision?

A person with normal vision, it seems, can see 7,000,000 colors. How many can a colorblind person see? I'm not as much interested in the exact number, or the technicalities that might exist due to ...
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1answer
79 views

Trying to understand reduction of color dimension in colorblind case

I understand that dichromats have one of their cone missing/not functioning. And as for Monochromats, 2 or all of their 3 cones are missing/not functioning. And I read from Wikipedia - Color Blindness ...
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1answer
122 views

What color does the other cone in Tetrachromacy correspond to?

Human with normal vision possesses 3 cones, which correspond to blue (S), green (M) and red (L). What about tetrachromacy, where people have 4 cones in their retinae? What is the fourth cone exactly, ...
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1answer
153 views

How many ommatidia does a honeybee have?

European honeybees (Apis mellifera) have compound eyes made of tiny facets called ommatidia. The number of ommatidia is usually known in most model insects, but I cannot find reference for the ...
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1answer
163 views

Firing rate of retinal ganglion cells

I have few questions about the firing rate of retinal ganglion cells. 1) How to explain the baseline firing rate if either the entire receptive field is stimulated or there is no light stimulus at ...
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1answer
104 views

At what minimum distance the direction at which eyes point becomes parallel?

This is very similar, but different than this question about focus, let me explain why it's not a duplicate at all.. That other question is about the distance of EACH individual eye FOCUS, this one is ...
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1answer
106 views

Deuteranopia confusion lines

For people with protanopia (absence of "red" cones), confusion lines look like this (which is quite intuitive for me) Analogous picture for tritanopia (absence of "blue" cones) But picture for ...
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3answers
118 views

To what extent can bacteria actually see?

I found some popular articles (e.g. nbcnews and iflscience) that bacteria can "see," but I highly doubt it's in the same way as people do just from looking at the limitations in the vision of small ...
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1answer
222 views

What photoreceptors are necessary to permit infrared vision?

Humans have red green and blue photoreceptors allowing them to sense colours in the spectrum of about 400-700nm. Certain proteins allow for the extending of wavelength range in the RGB receptors, this ...
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1answer
11k views

Why does my room suddenly look 'reddish'? My eyes seem to adapt to color

To get the context of this question clear, I would like you to walk through some parts of my house. We'll start with one of my rooms as it appears normally - As evident, this part of my house has a ...
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1answer
18 views

Why does white light viewed through optical chopper appear purple/blue?

I looked at a light like the one shown here through a fidget spinner (I believe I was observing near where the "blades" meet the inner portion) and noticed that it appeared purple/blue, particularly ...
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2answers
450 views

Seeing new colours with new photoreceptors

If we developed new "eyes" that could see "non-visible spectrum colours" and connected them to our brains, would our brain be capable of identifying and interpreting those new colours? Is our brain ...
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68 views

If longer wavelength color is perceived faster by human, what about non-spectral color (black)?

Related to human vision, I read the hypothesis about how longer-wavelength color is perceived faster by human eye than shorter-wavelength color source : A Brief Classification of Colour Illusions. But ...