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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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16 views

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
70 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
40 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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25 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 ...
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1answer
79 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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37 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
44 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
80 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
189 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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26 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
123 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
168 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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70 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 ...
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3answers
5k 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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54 views

What causes dreams to happen?

I've heard that dreams can be influenced by what happens in our daily lives. There are many theories about why we dream, but no one knows for sure. Some researchers say dreams have no purpose or ...
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1answer
70 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
160 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
188 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
35 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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0answers
39 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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0answers
25 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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0answers
331 views

What is the cause behind negative afterimages in our visual system?

Quoting Physiology of Behaviour by Carlson, 2013, The most important cause of negative afterimages is adaptation in the rate of firing of retinal ganglion cells. When ganglion cells are excited or ...
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1answer
83 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
29 views

What type of cells are we seeing in the blue field entropic phenomenon?

The blue field entropic phenomenon involves seeing the movement of immune cells passing over the retina. They are visible because, unlike erythrocytes, light can pass right through them. I am curious ...
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0answers
21 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
60 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
92 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
112 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
135 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
60 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
67 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
112 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
150 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
7k 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
283 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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0answers
64 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 ...
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1answer
194 views

Visual phototransduction, neurons depolarization when no light: why?

While reading into visual phototransduction I was surprised to learn that photoreceptor cells are actually depolarized when there is NO excitation (no light, i.e. when you see nothing, black) and ...
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1answer
118 views

Is it the theory of the 5 senses obsolete? [closed]

An enigmatic topic in traditional science was labelled as the mystery of the 5 senses, and how to best group senses by type. Is that theory now meaningless? Do Scientists still agree that that ...
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1answer
136 views

20/20 vision translated to resolution [closed]

What resolution and or DPI would a TV or VR headset need to be to equal 20/20 vision? and 20/10? With even the 4K TV it does not seem as sharp as my own vision.
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95 views

How do photoreceptors overcome the ambiguity of wavelength vs intensity to determine brightness?

I asked a similar question about the Principle of Univariance yesterday, but now I have another one. According to the Principle of Univariance, the input to a photoreceptor differs along two ...
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1answer
210 views

What is the neural coding of rod and cone cells?

In Rushton's paper on the Principle of Univariance, he states: Thus, though the rod input has two variables, wave-length and energy, the output differs only in one respect, namely 'brightness'. ...
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10 views

Tests for object size discrimination in mammals?

Are there common testing protocols for establishing whether an animal (mammals especially) can distinguish the size of objects? In particular, are there procedures or is there good literature on ways ...
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2answers
170 views

Can humans distinguish light having the same color but different spectrum? [closed]

Can humans distinguish light sources that have the same color in RGB space but having different spectral composition? I know one method, that is when the light is producesed by monochromatic laser, ...
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0answers
899 views

What is the field of view of humans (not just fixed angle eyes)?

What is the human field of view also counting the maximum vertical and horizontal eye movement (rotation), with the head still. It is unclear from this question whether the answer relates to the ...
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1answer
7k views

What is the minimal focal length of the human eye?

What is the minimum length to which the focal length of our eye can go, even when considering the blurred images too.
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1answer
67 views

What is a good set of notes to study human's eye mathematically?

I want to learn about the human eye. I could read a lot of online literature about it. However, ideally I would like to study human's eye by solving some maths exercises. I suspect people have done ...
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1answer
524 views

How do animals know who their child is?

This may be a strange question, but really it's something I've always wondered. Recently I was watching a documentary of penguins and how a mother penguin lost its child. Then it went looking for it, ...
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2answers
334 views

Cerebral activity during exposure to non - visible light

Our eyes only have the ability to sense light within a certain spectrum. My understanding is that particular frequencies energize specific cells in our eyes, each responsible for a different "color". ...
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1answer
2k views

Telling distance with one eye

Basic mathematical/logical reasoning makes it clear that you need two eyes to have depth of vision. By seeing an object from two perspectives, our brain can calculate the distance of the object based ...