How human beings can see color?

Human sight

The sight is one among the five senses human beings dispose of. It makes possible to perceive the light stimuli, hence, figures, colors, sizes and location of objects in the space, through the eyes.

Visibility range is associated to the human eye. It contains the range of the electromagnetic spectrum where there are all the colors, components of the light, visible to the eyes.

On this way, consequently the photoreceptors placed on the retina can convert light into electrical signals; they are sent through optic nerve to the brain for being processed; the wavelength and the intensity of the light source affect the photoreceptor’s response.

The sight organ is equipped with photosensitive receptor :  rod cells, responsible for perceiving shape, shade and movement, and cones, responsible for seeing colors.

Human beings can see a frequency of wavelengths from 390 to 760 nanometers. This visible spectrum is a very little part of the entire scale and it is located just after the infrared rays and before the ultraviolet frequencies.

The commonest visible spectrum existing in nature is the solar radiation, represented by the rainbow that manifests itself as an atmospheric phenomenon whenever some drops of water, remained in suspension in the air, are passed through by sunbeams.

The subdivision of the colors in the visible spectrum is the following (from the shortest to the longest) : Violet, Indigo, Blue, Green, Yellow, Orange and Red.

Mixing up two or more different colors is the method to obtain new colors’ hues. It’s interesting the fact that while all these colors are reflections of light, black is not. Black is not a color, in fact, it is the absence of light: it does not have a specific wavelength.

Similarly, white is not considered a color because it comprises all hues on the visible light spectrum, containing all the wavelengths.

Thus, black and white in a technical sense are shades; traditionally people used to refer to them as colors, but black is often a massive pigmentation due, for example, to ink and not to the light.

To understand how light allows us to see, it’s important to underline that what we really see as objects is that part of light reflected by them, meanwhile the other quantity of light is partly absorbed.

According to it, a yellow tulip would absorb all the micro electromagnetic waves except those corresponding to yellow microwaves that are those going to be reflected and seen. Black objects absorb all wavelengths in the visible light range and when an object is white, it means that all white light is reflected from it.

Nothing can be pure white or pure black in nature.

In space, there are far more possibilities to encounter pure black and white colors, a black hole is an example due to its awful force of gravity to absorb light.

Human beings’ sight color vision problems

The most known visual defect referred to the difficulty to see colors or to see differences among them is the color blindness, also called, color deficiency. It usually affects both eyes, equally remaining stable throughout life in a major ratio for males than females. It is due to the dysfunctional structure or absence of one or more among the three types of cons, those that allow us to see green, blue and red colors.

The brain uses the inputs, prompting from these cone cells in order to determine the individual’s color perception.

This condition is genetical and more likely to be inherited from mother to son. According to the gravity, it could be light, mild or severe, but it does not affect the sharpness of the vision unless in critical severe situations. A significant change in the way of perceiving color is the outcome of far more serious disease conditions. It might be acquired by the use of some drugs or chemical substances, as styrene, or organic solvents.

It’s claimed that this defect affects more men having Northern European descent. However, it is a worldwide phenomenon and in some cases even invalidating. Indeed, there are some countries in which people affected by color deficiency are not allowed to be eligible for some jobs, among them: crane operators, designers, aircraft pilots, train drivers and armed forces.

Colors, whose concerning is strictly related to this congenital condition, are primarily red and green, following in a second instance blue and yellow.

Do people see colors in the same way ?

A question rose numberless times with no reliable responses, because of the several components of which it could be made up of. Nevertheless, the vision itself may be almost identical what differs is the brain’s perception of the color in our neurological and cognitive system.

Consciously entails a great effort to explain why one color like or not, or just wondering why one is found more attractive than another, passing from what that color has meant in our background in life to which unconsciously sensations it bring about with any aware reason.

A single image looked through gives subjectively different prompts. Considering that a color for example the brown eye color could be categorized into various subclasses of brown, including hazel, honey, cocoa, chestnut, russet brown, having each one their own hallmarks dependently attached as brightness, depth, structural facets and the capacity to fit to weather atmospheric environment even making change the perception of the iris color thanks to the higher or lower light levels then results clear to classify the human vision as not a steady but a dynamic perception.

Do animals can see colors as much as human ?

The human’s vision is in itself unique. Primates have the best color vision of all mammals and human’s is the most efficient among primates. Human beings possess trichromacy as well as several marsupial do.

Outstandingly, reptiles and amphibians have four, occasionally five, cone types that allegedly, make them able to see more colors than human. To be noted, crocodiles have a very good eyesight whether day or night, keener at night, and, differently to human due to their horizontal receptors, they can focus on a panoramic view instead of a focal point; the only blind point is directly behind them.

Dogs and cats have dichromatic vision, for their 2 types of cones. Dog’s color spectrum is limited to shades of green, brown, yellow and blue; cats need just a little of dim light to see well at night, because of the high number of rods in their retina but, during the day, the detection of the wavelengths entails the blue-violet and yellow-green ones, not including red and orange.

Geckos have no rod cells but, out of it, they have developed their cone cells to become more rod-like, allowing them to see more than 300 times better than human by night.

Birds are sensitives to ultraviolet range as well as bees and many other insects. If human based the perception of the colors on three basic colors red, green and blue; on the other hand, bees based their colors on ultraviolet light, blue and green.

It is believed that one of the most beautiful vision of the world is owned by butterflies; they possess fifteen full types of cones by which their view is a remarkable color of patterns; from it, also the wonderful colors on their wings.

Some species of the snake family are recognized to be able to see in infrared; as a thermo-scanner they detect the heat thanks to special pits, they can feel approaching warm sources, eventually preys.

Many species of fish can see the ultraviolet end of the spectrum, beyond the violet.

Most of the marine mammals are monochromatic; whales and dolphins are also thought to be color blind. According to it, sharks have a bad sight in spite of being one of the most dangerous predators; 10 out of 17 species of sharks haven’t been found to have any cones at all. It means that their capacity to discriminate colors is quite absent. They are supposed to have only a rod to detect a single microwave of light. The vibrations or the pulses in the water are effectively what sharks perceive;

COLORS

The first color wheel was created in 1666 by Isaac Newton. He claimed that by having blue, red, yellow and adding black and white, it should be possible make a whole rainbow of colors.

Many important scholars about color perception have assumed that three “pure” primary colors can mix into all possible colors but it is not the case. In art, the three primarily colors that can’t be reduced into others are : YELLOW, RED and BLUE.

Three real “primary” colors of paint or ink can mix only a limited range of color, called a gamut.

Here, the secondary colors stemmed from first colors’ mixing:

BLUE+YELLOW  makes GREEN

RED + BLUE makes PURPLE

YELLOW+RED makes ORANGE

The International Commission on Illumination (CIE) uses 3 attributes to classify colors: hue, brightness and saturation.

Topics on color are usually simplified but the truth is that although the eyes can distinguish around 100 color shades, reaching 1 million of possible combinations, this number is pretty unrealistic if compared to the narrow range of colors humans ordinary see.

There is a point in claiming that nowadays main categorization colors’ models, RGB and CMY, are insufficient and they are compensated pragmatically by the color production including printing, paint, varnishes and inks.

In fact, the expression of a color in nature is a complex event to which we can only experience always remembering that what we see is a perception, sometimes even wrong, set up by our brain.

Colors are, somehow, an unknown galaxy yet, but it does not prevent us to really enjoy all these wonders that keep on amazing and wondering.

If you want to read more about perception, art and “Refractions”, you can click here.