What is the normal range of vision of a person and what is the range of perspective of the human eye

The farthest distance a person can see the sea s (unit: km) on a clear day can be estimated using the formula s squared = where h is the height of the eye from sea level (unit: m).If a person stands on the shore and observes, he can see when the eye is at the height of the sea level.

Human eyesight is different, normal people's eyesight, photopic distance is 25cm, 4km away from the scenery is not easy to see, when more than 500m, there is a blurred image of the scene, the distance is shortened to 250 270m, the outline of the scene can be seen clearly, if you want to identify the species of flowers and trees, it should be shortened to dozens of meters.

There is a limit to the range of human vision, and the average distance to see a fighter jet in the air is about 8 kilometers, which is the average on a clear day. When there is fog, rain, and dusk, visibility is very poor, and the distance you can see is greatly reduced. And everyone's eyesight varies greatly, with some pilots being able to see an airplane from 20 kilometers away, while others not being able to see as close as 8 kilometers.

In addition, it has a lot to do with the size of the aircraft, and for the bomber you can see a little farther. There is another feature of the naked eye, if you have seen the aircraft, keep staring at the plane and let the plane gradually fly away, you can not see it after more than 10 kilometers. On the contrary, looking for an airplane in the sky, sometimes it has flown to a distance of 5 kilometers and cannot be found.

8 km is currently a generally accepted (and not explicitly defined) value.

Of course: a pair of normal eyes with a visual distance of infinity. At night, you can see the moon 380,000 kilometers from Earth, and even stars hundreds of millions of light-years away.

But the resolution of the naked eye is limited, and the difference is very large. According to tests, the resolution of people with normal vision is about 1 in 2,000 to 1 in 5,000. For example, if you are standing next to the *** Memorial Hall in Tiananmen Square, Beijing, 400 meters away from the national flag, if you can see the top of the flagpole with a diameter of 20 centimeters, your eye resolution will be 1 in 2,000.

In this way, when you take an airplane and look down at the ground at an altitude of 10 kilometers, you can clearly see the railways, highways and the Great Wall with a width of more than 5 meters.

You see things because the emission of light from the surface of an object, and the refraction of light in the air, has little to do with your eyes.

It's hard to say, different people are different, theoretically it's the close point of the person to the infinity.

Perspective refers to the angle from which a human, animal, or lens can involve, photograph, or see. The narrower the visual field (the smaller the angle), the smaller the field of view or scenery that can be seen without moving the eyes, which means that small objects can be seen clearly. The opposite is true for wide viewing angles.

The angle formed between the center point of the lens and the two ends of the diagonal of the imaging plane is the angle of view of the lens core, for the same imaging area, the shorter the focal length of the lens, the larger the angle of view. For a lens, the angle of view mainly refers to the range of angle of view that can be achieved, and when the focal length becomes shorter, the angle of view becomes larger, which can shoot a wider range, but this will affect the sharpness of the subject from a distance. When the focal length becomes longer, the angle of view becomes smaller, which makes distant objects clearer, but the wide range that can be photographed narrows.

Humans are usually 120 degrees, and when focused, it is about one-fifth, or 25 degrees.

The angle of view of the fisheye is close to 180 degrees, and the eyes on both sides must have a total of 360 degrees.

The falcon has to search for and target small slippery animals at high altitudes, and Lee Cover digs its eyes to allow for two perspectives. The angle of view is wide when searching and narrow when aiming.

The static contrast ratio of the retina is about 100:1 (the focal ratio is about. When the eye moves rapidly (nystags) it repeatedly monitors the chemicals it is exposed to and geometrically positions to adjust the iris to control the size of the pupil.

When you first come into contact with a dark environment, it takes about 4 seconds to fall into complete darkness; Through the chemical adjustment of the retina (Purken page effect) it mostly takes 30 minutes to fully adapt.

At this point, the dynamic contrast ratio may reach about 1,000,000:1 (focal ratio is about 20). This process is non-linear and multifaceted, so if it is interrupted by light, the adaptation process must be restarted.

Complete adaptation is dependent on good blood flow, so dark adaptation may cause a large burden on blood circulation (anemia) as if under the influence of alcohol or tobacco.

In the pure air, the human eye can see a candle 27 kilometers away. Ships can be seen from 6 to 25 kilometers away from the sea. If you are on the top of a high mountain, your vision can expand to 320 kilometers.

If you look up at the starry sky, you can see artificial satellites 1,000 kilometers away, and you can also see constellations tens to thousands of light-years apart.

Here's what you might use in your life – estimate how far away you are from these vaguely recognizable objects:

Target distance.

Multi-storey buildings 8 km 10 km.

Bungalows 5 km to 8 km.

House windows 4 km.

Single person 2 km.

Cap 400 meters.

Eyes, nose, fingers 60 meters.

The visual distance of a normal person is 300 meters to 500 meters. The resolution distance of farsighted people can reach 700 meters to 800 meters.

Of course, some people are gifted, and the possibility of seeing farther is not ruled out.

Under normal lighting conditions, the most convenient and habitual working distance for normal eyes is called photopic distance, which is equal to 250mmGenerally, the near electrical distance of the eye is less than the photopic distance, and after the age of 45, the near point distance of the eye is greater than the photopic distance, which is called presbyopia.

It's like being able to see the sun, as long as there's light big enough and theoretically infinite.

The angle at which the human eye can see the object in front of it at the same time is called the viewing angle. Arranged from small to large, there are 5 sub-categories:

a. Monocular perspective. One eye, looking straight ahead, the eyeball cannot be moved, and the head cannot be moved forward. Then (taking the right eye as an example) 50 degrees is visible above, 70 degrees below, 60 degrees on the left, and 100 degrees on the right.

B. Same as above, but the head can be moved. In this way, the visual range of the eyeball can be more fully expressed, and the occlusion of the eye frame and nose can be removed. As a result, 55 degrees are visible above, 75 degrees below, 60 degrees to the left, and 100 degrees to the right.

Curiously, there is no change in the left and right angles.

c. Same as a but binocular perspective. The upper and lower angles are the same (120 degrees in total), and the left and right angles are 100 degrees (200 degrees in total).

d, the same as b, but for the binocular perspective. The upper and lower angles are the same (130 degrees in total), and the left and right are 100 degrees (200 degrees in total).

e. Monocular perspective, the eyeball can be rotated, but the head cannot be moved. Then (taking the right eye as an example) 70 degrees is visible above, 80 degrees below, 65 degrees on the left, and 115 degrees on the right.

f. Binocular perspective. Same as above, but for both eyes, the top and bottom are the same (150 degrees in total), and the left and right are 115 degrees (230 degrees in total).

g. Fixation perspective. Binocular eyes, the head can not move, the eyeballs can be turned, and the visual center can reach the range. 40 degrees above, 50 degrees below, 55 degrees on the left and right.

In these perspectives, c represents the maximum range that can be seen inadvertently, used as an instinctive "precaution" for animals; f represents the maximum range that can be perceived when the head is not moving, and is used for the animal's instinctive "attack".