Everyone has limits, for example, how fast he can run or how long he can stay without water. But what about the limitations of our five senses, which in essence are the tools we use to perceive our environment?
Approximately one quarter of the brain is involved in visual functions, so the sight is unquestionably the most important sense for our perception of the world.
1. The visible spectrum
It is certainly the most well-known limit of our senses. The human eye recognizes light with a wavelength between 390 and 750 nanometers. At the same time, some animals are able to perceive light at other wavelengths.
2. Visual field
Healthy eyes have a visual field of about 200 degrees from right to left. About 120 of the 200 degrees are shared by the two eyes, creating the binocular vision. Vertically the field reaches 135 degrees (which decreases with age). And that’s because the eyes are located in front of the head and not sideways.
Eyes on the side of the head are common among species that are mainly prey raptors. They have a larger field at the cost of a smaller binocular vision, which provides them with the ability to feel the predator with greater ease with the help of their extended visual field, but not to see it specifically.
3. Angular resolution
It is one of the terms that describe the ability of the optical organ to distinguish fine details.
The measure unit is arc minutes (and seconds), which corresponds to 1/60 (and 1/3600) of the visual field degree.
The human eyes have usually angular resolution equal to one minute (with a few seconds more or less). If you are drawing a line with a thickness of one third of a millimeter and are keeping it at a distance equal to your hand, you are covering one arc minute of your visual field.
4. Blind spot
The human eye is internally covered with photoreceptor cells that perceive light. The received information is transferred to the brain via the optic nerve. However, the problem is that the optic nerve passes from the “overlap” of photoreceptor cells, creating a point that does not detect light.
Normally it is not a big problem. We see with both eyes, while our brain is very good at using the obtained information to complete the picture, i.e. the gaps created by the blind spots. But things get worse when you need to rely on only one eye.
To see how the blind spot works try this illusion:
Close your left eye and focus on the small dot that is not moving. While the large dot is moving, it will reach a point (the blind spot) where it will not be visible.