7
votes
1answer
856 views

Dark veil when getting up too fast

I was asking myself this weird question. When you get up or stand up too fast, sometimes, you see something like a dark veil, and you aren't able to see anything distinctly for 2 or 3 seconds, then ...
2
votes
1answer
25 views

What is the focus distance of a 3D screen?

I've thought long and hard about wheter this is the appropriate section for this question, because I guess it's kind of an interdisciplinary subject. My understanding of stereopsis (please, correct ...
2
votes
1answer
105 views

Why don't we have more cone cells (bigger fovea)?

Background Apart from being able to sense color, cone cells are able to perceive finer detail and more rapid changes in images, because their response times to stimuli are faster than those of rods. ...
1
vote
1answer
151 views

Is it safe to look at infrared LEDs?

What happens if one looks directly at infrared LEDs? Sometimes I see this kind of LED at night as red dots and I'm also courious about it. I was wondering what would happened if one looked directly ...
3
votes
2answers
118 views

Why do our eyes “wrap” hue from UV to IR?

On the high-wavelength side of things, we see almost-infrared as reddish, with a slight tinge of magenta. On the low side, we see violet fading into the same magenta color. Why is that? You can see ...
10
votes
1answer
122 views

Are there specific conditions that allow humans to see ultraviolet wavelengths

It is fairly common knowledge that the lens in its normal state absorbs ultraviolet (UV) radiation. An interesting notion has come up from time to time in my reading that suggests there are a small ...
5
votes
0answers
224 views

Reason for seeing grid-like patterns when strobing a solid black-white image?

I was trying to do some stimulation for SSVEPs by strobing a solid black square and a solid white square. Weird thing was, I ended up seeing weird grid like patterns that looked like this, always of ...
4
votes
1answer
112 views

Are these claims of “revolutionising” understanding of human vision and hearing valid?

I've started a hobby machine vision project (and posted some questions to this end on other SE sites) and on a side track, also been looking at relevant research in human vision (and partly, hearing). ...
1
vote
1answer
139 views

Why are trichromat cone cells unable to sense ultraviolet and infrared radiation?

I understand that cone cells vary in the color they sense, is this because of wavelength, frequency, something else, or a combination of the previous? I also understand that tetrachromats can see an ...
4
votes
3answers
134 views

Is it technically possible to make someone see something when their eyes are closed?

I'm writing a little article and need any information about how human vision works and latest technologies and discoveries around. Actually its not a professional article. Its for a group of my ...
7
votes
3answers
662 views

What is the difference between a circular and a cat's-eye pupil?

I've been to local zoo the other day and one lizard caught my attention: its pupils are circular, which, I thought, is not usual for reptiles. Turns out it is, but now I can't find any explanation on ...
4
votes
1answer
51 views

HSL Lightness vs Eye sensitivity

In a monochromatic spectrum, is the human eye equally able to distinguish between lighter colors just as it is in distinguishing between darker colors? I mean is there really a linear relationship ...
8
votes
1answer
170 views

What are the “stars” we see after a bump on the head?

Sorry if this might appear funny. When I close my eyes for a longer time, and suddenly open it, I see some twinkling white small circles, and when i concentrate on anyone of them it disappears, as ...
9
votes
2answers
24k views

Which shades/hues of color are easiest to distinguish for humans?

I'm trying to represent data graphically and am using a variation of hue/lightness to distinguish one data point from the next. I would like to use a color that would allow me to convey most ...
2
votes
1answer
270 views

Can visual acuity be improved?

Is it possible to completely cure myopia using natural methods (i.e. not with Lasik etc.)?. I have seen websites claiming that exercising the eyes will help improve eyesight. Is this true?
5
votes
2answers
442 views

Why does squinting allow you to see objects more clearly?

How does squinting alllow one to see clearer pictures? What are the harmful effects?
4
votes
1answer
53 views

Does retinal detachment happen more frequently at night?

My understanding and experience is that during the night photoreceptors are less tightly coupled to the retinal pigment epithelium. Does this make it more likely for a retinal detachment to happen at ...
9
votes
1answer
353 views

Why does this illusion work?

This is another image I found on Google+ All lines are absolutely straight, parallel and perpendicular but why does it appear to have a curvature? Related: How does this illusion work?
2
votes
1answer
2k views

What negative effects can pinhole glasses have on the body?

While shopping in the local supermarket yesterday, I was surprised to find this display on one of the shelves. I also realize that I should have taken a pamphlet with me, as well as a picture of ...
1
vote
0answers
176 views

How do optical illusions work? [closed]

Hello fellow investigators I have two questions about optical illusions 1) A photo mosaic is something like this http://i.stack.imgur.com/Pzplp.png What are the optical principles behind our eye ...
8
votes
1answer
881 views

How does this illusion work?

I found this image on Google+ If you shake your head you can see a portrait of a person. Can anyone explain how the image is constructed in the brain?
11
votes
2answers
447 views

When did vision evolve for the first time?

Today I wondered what the first organism to evolve vision would have been. I assume that it would have been kind of primitive and basic, but of course extremely innovative and eventually useful to a ...
55
votes
4answers
1k views

Is there a reason why human eyesight and plants make use of the same wavelength of light?

The accepted range for the wavelengths of light that the human eye can detect is roughly between 400nm and 700nm. Is it a co-incidence that these wavelengths are identical to those in the ...