What is the averange range of unaided human vision?
483079
There is no single correct answer, and the useful answer is not found when discussing 'range.'\nHuman acuity is what you are curious about. This is a function of the sensitivity of the central retinal cells, the 'macula' which is the spot that sends detailed information to the brain. The more cones you have in the macula, and the more perfect the curvatures of the cornea and lens, the better your vision will be. \nThe best descriptor to use when seeking the best vision that people can have, the most important parameter is angular detection. In modern terms this would be the size of the pixels that the eye can detect. The smaller the pixels that can be sensed, then the farther away an object can be and still be seen. \nThe common reference for angular detection is called the 20-20 scale. It just means that if a person is 20 feet away from a character such as a letter 'E' of a certain size, can he tell if it is an E, or does he think it is a B or an H. The sharper the sensitivity of the eye, the smaller angular detection, then the farther away the 'E' can be and still be recognized.\nThere is a famous fighter pilot in WW II who could spot enemy airplanes farther away than most of the other pilots. He  says in his biography that he could actually see the machine gun bullets as they shot away from his plane toward the enemy plane he was shooting at. He became an 'Ace.' His name is Charles E. Yeager. He is also the first man to fly faster than sound.
1089258
For one, cameras today can't produce the resolution that a human eye can produce.\n\nThey are working on artificial eyes and radar, and I think a Retinal Transplant might help you. Talk to your doctor about if you are a possible candidate.
534267
You won't find them with a -2.75 BC (base curve).  -2.75 is the power.  The base curve will be a number like 8.3 or 8.6.  If you're confused about your prescription, you should talk to your eye doctor.
575563
If it's perfectly flat (Remember the earth is curved), you can see forever.. Stars are a LONG way away, and there is a plane (ok an infinate numbers of planes) that connect you and that star.. Which is the same as "perfectly flat" ground.\n\nNow, Seriously:\nFor someone who is 5' 4" (eyes 5 feet from the gorund) you can see: 3.0097474977147174 miles.\n\n-HtJ
913461
"Near Infra-Red" starts at 750nm wavelength (a fixed, accepted value).\nIn theory, and by definition, we CAN'T see it.\nHowever, we are all different: we are not machines built on a standard.\nTo find out if you can see NIR, you have to go to a laboratory, ask for a calibrated source of light and check from say, 650nm to 900nm wavelength radiations.  You will then be able to find exactly your limit for "your" visible.  If it is above 750nm, then you see NIR... officially!\nYou can compare this to your auditive perception: the AF (audio frequencies range, by definition, from 16Hz to 16000 Hz).\nMany of us cannot hear 16kHz, many of us can hear much higher than that!\nIt is all relative.
610977
You need to have two eyes to determine distance.  Basically, if you close one eye, you can still see, but when light hits your retina, it's all in a single plane, so even though your brain tries to add depth, it's basically getting a flat image.  But with two eyes next to each other, you can tell how far away something is based on how much is location relative to other objects changes in the information you're getting from each eye.  If something is further away, the distance between your eyes isn't going to make much of a difference to it's location on the retina, but if it's closer up, it's going to make a lot more difference.  The brain uses the information it gets about these differences to determine how far away an object is.  If you only had one eye, you'd be able to see objects, but you wouldn't know where they were, so you'd bump into walls all the time!
521771
Red.  It is of relatively low frequency in relation to other discernible colors, and has a wavelenght between 630 and 760 nm.  That is the only way you can expalain a color to a blind person if they were blind from birth.
123325
Yes, think stars.  VISION doesn't travel; LIGHT does.  So the question is how far can light travel, and there are no real limits to this--apart, perhaps, from the fact that light gets stretched by the expansion of the universe, and the red-shift "horizon" is at about 14 billion light years away.  But since there is nothing bright enough that the unaided eye can see, in practice it's less than that for things you can actually--rather than theoretically--see.
752656
The size of an object you can resolve with an optical system has a theoretical limit given by the wavelenght of the light you're using divided by the diameter of the optics multiplied by 1.22. If you plug the numbers in you find for a 1 foot diameter optical system at visible light (~400 nm) at an altitude of 100km, the smallest thing you could see is on the order of a foot, give or take (rough calculation). You could definitely not read a postage stamp or a wrist watch. Maybe a license plate with some bigger optics, but this is ignoring all sorts of atmospheric scintillation which screws things up.
367356
Depends on the water.  In water near the beach or a river mouth, visibility may only be a few feet.  Out in the open ocean, in areas of low productivity, light may be visible to the naked eye for hundreds of feet underwater, though probably no more than ~400-600 feet at best.
55192
What happens when we do the math?  Lets see... I will go with distances of 20 feet and 40 feet respectively.  Lets say the center line of the person standing next to us is two feet from our center line. So at 20 feet we have a 5.7 degree shift of the eye.\nhttp://www.google.com/search?q=sine(2+feet+/+20+feet+)+in+degrees\n\nAt 40 feet we have a 2.9 degree shift of the eye.\nhttp://www.google.com/search?q=sine(2+feet+/+40+feet+)+in+degrees\n\nNeither of those seem that unreasonable for our amazing optical processors to detect.  Also it is quite likely that the person actually did look at you at least for a moment, probably even more than once.  You should at least be able to detect the direction of rotational shift of the eye as they return their focus to the person standing next to you.\n\nThe human eye is even able to take snapshots of very fast moving objects.  I have even done this with rain while looking out the window of a passenger jet traveling at roughly 500 to 600 miles per hour.\n\nSurely detecting eye an eye aim change of 1 degree or less at 40 feet or even slightly farther is not any more difficult.
35615
As long as ur vision is not affected..\n\nCheck with ur dr for any eye disease or other medicaclcondition.\n\nthere is usually a subtle difference in the size or symmetry between the two eyes\n\nIt looks awesome. i havent seen anyone with that kind of face.
29315
You could just ask them like you would ask anything else.For ex: What is your eye perscription?People have asked me this before and I have never been offended.I know that I'am legally blind with out contacts or glasses.People I realize are just curious,If you are trying to tell someone what your eye perscription is you would say ex:20/40 That means what most people can see at 20 ft, you think is 40ft away causing it to be out of focus and so on.Once you get passed a certian number they don't really use those terms .They just tell you you're legally blind w/o contacts or glasses.  You have exstremely bad eye sight  and can't drive or work or do much of anything without these.Hope this helps you:)
55659
Most people have some degree of astigmatism.
222377
+0.25 isn't very much power, but it might affect you.  If you think it's too much, go back to your eye doctor to have him/her verify the prescription.  (Don't expect to get a free complete eye exam, though.)
596229
Hi there,\n\nThe viewing distance from the screen to the eyes should be seventeen to twenty-six inches. \n\nSome eye relaxation exercises would also help.\n\n:)
445171
if you are nearsightedness this sight will probably help you.\n\n\n\n\n\nreversingnearsightedness.com