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Color Basics Knowledge- Object Color Rendering
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Why use Color Rendering instruments? We can see colorful colors during the day, but at night all objects turn black. How is the color presented? What are the factors related to?
First of all, different objects will have different colors, so the color must be related to the properties of the object itself.
Then, in different light environments, the same object will have different colors, such as the apple below, the color is different under the light and the daylight, which means that the color is related to the light source.
Finally, different people see the same object, there will be different feelings, so the color is also related to the human eye.
It can be obtained that the color representation of the object is related to the attributes of the object itself, the light source, and the human eye. As shown in the figure below, the light source is illuminated on the apple, and the human eye feels the color of the apple.
First, the light source
Scientific definition, light refers to all electromagnetic spectrum, which can be divided into radio waves, infrared rays, visible light, ultraviolet rays, X-rays, and γ-rays according to the wavelength, as shown in the figure. The wavelength of light that the average human eye can accept is between 380 and 760 nm.
Electromagnetic spectrum
The sun is the largest source of light for humans. More than 99% of the solar fusion radiation spectrum is between 0.15 and 4.0 microns. The solar spectrum is shown in the figure. These bands are affected by atmospheric attenuation. Most of the visible radiation can reach the ground. Most of the ultraviolet radiation is absorbed by the ozone in the upper atmosphere. The solar radiation energy reaching the ground is much smaller than the upper boundary of the atmosphere. The visible spectrum is about 40%, and the infrared spectrum is about 60 %, the amount of ultraviolet light is extremely small.
Solar spectral distribution
Different light sources have different spectral distributions, such as incandescent lamps, blue light and red light have different compositions at different wavelengths.
Second, the object itself properties    
When light strikes an object, light is transmitted, reflected, and scattered. When light strikes a transparent object, most of the light penetrates the object, and only a small portion of the reflected and scattered light. When light is illuminated as a non-transparent object, most of the light is reflected and scattered, and almost no light passes through the object. Different objects have different properties such as transmittance, reflectance, and refractive index for each wavelength, and thus exhibit different colors. The color of a transparent object is determined by the light that passes through the object, while the color of a non-transparent object is determined by the reflected and scattered light.
For example, the blue sky is when the sunlight enters the atmosphere, the longer wavelength light, such as red light, is transmitted to the ground through the atmosphere; while the short wavelength purple, blue, and cyan light encounters atmospheric molecules, ice crystals, water droplets, etc. , scattering occurs. The scattered purple, blue, and blue light fills the sky, making the sky appear blue.
When the sky is filled with tiny water droplets after the rain, when the sun shines on these small water droplets, different wavelengths of light scatter into the sky at different angles, forming a rainbow.
Third, the human eye    
The eye is an optical system consisting of the cornea, iris, lens, ciliary body and vitreous. The structure of the eyeball is shown in the figure. The retina with blind spots and macula is a part of the sensitization and signal processing that forms a key part of human vision; the optic nerve and brain are signal transmission and display systems. Since light having a wavelength of less than 300 nm and a wavelength of more than 1400 nm can be absorbed by the cornea, the anterior chamber, the lens, the vitreous body, etc., the wavelength of the light radiation reaching the retina is in the range of 300 to 1400 nm.

eye structure
The light reflected from the external object passes through the cornea, pupil, lens and vitreous body, and is refracted by the lens or the like, and finally falls on the retina to form an object image. There are light-sensitive cells on the retina. These cells transmit image information through the optic nerve to a certain area of the brain, and the person produces vision. The process of visual formation can be expressed as shown in the figure.

vision formation
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