Pigment
Pigments are substances that determine the color of objects by absorbing and reflecting specific frequencies of light. The human eye perceives these colors based on the wavelengths that are reflected, while others are absorbed. This interaction is essential for processes such as photosynthesis, where pigments like chlorophylls allow plants to convert light into energy. There are three primary classes of natural pigments: chlorophylls, which are predominantly green; carotenoids, which appear in shades of red, orange, or yellow; and phycobilins, which exhibit blue hues. In addition to their biological significance, pigments play a vital role in art and design, where they are used to create dyes and paints. Artists historically sourced pigments from a variety of natural materials, including rare insects and precious stones, while modern formulations often utilize synthetic pigments for a wider range of colors and durability. Understanding pigments is essential not only in biology and ecology but also in the fields of art and material science.
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Pigment
Pigments are substances that absorb and reflect specific frequencies of light. These frequencies are interpreted as colors by specialized parts of the human eye. Objects appear as the color or colors they reflect least. Pigments and their relation to the absorption of light are incredibly important to photosynthesis. Additionally, certain pigments have been harvested or manufactured for use in paints and dyes.
Light, Color, and the Eye
All color comes from the reflection of light. Some ancient Greek philosophers believed that all objects emitted rays of light. They thought that the light emitted by objects was received by the eyes, which processed the light and reflected the color. In reality, all natural light is emitted by the sun. It travels to Earth, reflecting off every object, and eventually makes its way to an observer’s eyes.
Light enters the eye through the cornea, the clear window at the front of the eye. The cornea focuses the light into the lens, which further focuses the light toward the retina. The retina is a layer of sensitive, specialized cells at the back of the eye. The light hits the retina and is received by tiny reception nodes called rods and cones. The rods and cones catch specific frequencies of light, interpret them, and send those interpretations to the brain through the optic nerve.
Different frequencies of light are interpreted by specialized sets of rods and cones as colors. What individuals see as white light actually contains every color. This can be observed by shining white light through a prism. A prism is a clear structure specifically designed to split light into its various frequencies. When a beam of white light is shone through the prism, it emerges as a rainbow.
When white light hits an object, most frequencies of the light are absorbed. What cannot be absorbed is reflected away from the object and is then interpreted by the eye. Thus, objects appear as whatever color of light they cannot absorb. For example, a red cup absorbs every color of light other than red.
If the rods and cones in the eye are damaged, an individual’s perception of color may drastically change. Some people are born color-blind. These individuals are unable to see certain parts of the color spectrum. In most cases, color-blind individuals are unable to see a specific color. They may not be able to distinguish between two colors, or one color may appear as another. Most color-blind individuals do not see in gray scale, or tones that range from black to white through varying shades of gray.
Some animals can see light frequencies invisible to humans. This area of the spectrum is called ultraviolet light. Too much exposure to ultraviolet light is harmful to humans.
Pigments
Pigments are substances that absorb specific sections of the color spectrum. They are normally charted along the RGB (red, green, blue) spectrum. For example, blue pigment reflects blue light frequencies but absorbs red and green light frequencies. When a pigment reflects all light frequencies, it appears white. When it absorbs all light frequencies, it appears black.
Most naturally occurring pigments can be sorted into three primary classes. Chlorophylls absorb red and blue light, thereby appearing as green. Chlorophyll is found in plants and algae. While there are several common chlorophylls, the chlorophyll a variety is the most important. This is the specific variant that allows plants to harvest sunlight, making photosynthesis, or the process used by a green plant to turn water and carbon dioxide into food when the plant is exposed to light, possible. The second most common variant, chlorophyll b, is also used in photosynthesis. However, it occurs in a much smaller variety of plants.
Carotenoids, the second major naturally occurring pigment group, also are found in plants. They tend to appear red, orange, or yellow. The orange color found in carrots is a common example of carotenoid pigments. While carotenoids are involved in the photosynthetic process, they cannot store energy and are not as crucial as chlorophyll to a plant's existence.
The third group of natural pigments are phycobilins. These pigments appear blue and are only found inside cyanobacteria and rhodophyta. They are excellent at absorbing light frequencies that chlorophyll tends to reflect.
In the art world, pigments are any substances that can be used to make colorful dyes and paints. Artists value pigments that have vibrant, stable colors that last for long periods. In the past, artists used large numbers of exotic materials to create exotic colors. Some artists used the shells of rare insects to create a brilliant red hue. Others used resins, saps, tree gums, ground up precious stones, and vermillion to create varying pigments. In the modern production of artistic materials, chemists use synthetic pigments to give paints and dyes their color, providing a variety of tints and hues that do not occur naturally.
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