Basic knowledge for a color mixer
I. Basic knowledge of colors
1. Three factors in forming a color
Light, object and eye
Color is the light ray seen by naked eye and it is generated by electromagnetic wave of a very narrow range of wave length (visible light, wave length 390nm-770nm). The electromagnetic wave of different length is showed as different colors, and the recognition of colors is a feeling of optic nerve generated after being stimulated by the radiant energy of electromagnetic wave. At the same time, the different colors we feel are closely connected with the observant and the observing environment (because our eyes and brain have very strong adaptability and can adjust themselves to the changing environment).
Recognition of color shall meet three conditions:- one object; -light source (if the object is a luminophor, no light source is needed);- the observer summaries his/her feelings to the color.
Color is a kind of visual effect to light which is generated through our eyes, brain and our life experience. People's feeling to a color is not only determined by the physical properties of the light, because people's feeling to a color is often affected by the surrounding color. Sometimes, people also directly call the physical property of generating different colors as color. (@ Qimao Application Elite Circle, the First We-media in the Industry)
Composition of color:
Red Orange Yellow Green Cyan Blue Purple
Black White Gray
2. Factors affecting color judgment
(1) The difference of light source
Under different light sources like sunlight, fluorescent lamp and osram lamp, the same object looks different. Therefore, the national GB 9761-88 has detailed stipulations on visual colorimetric judgment. Natural light or artificial daylight can be used in color comparison.
Natural light is the light ray in partially cloudy northern sky from three hours after sunrise to three hours before sunset. The light shall be even with illuminance no less than 2000lx.
Artificial sunlight adopts the color comparison box with illuminating source similar with CIE-standard illuminant D65 spectral energy distribution, with the illuminance of color comparison location within 1000～4000lx. For color comparison of darker colors, the illuminance shall be larger.
(2) The difference of observers
Sensibility of people's eyes always has difference. People who think their color vision is normal can still have recognition bias on red or blue; vision will also change as people get older. Due to all these reasons, the same color seems different to different people. To avoid eyestrain, after comparing color with color table with strong colors, do not compare the light color table with complementary color sample; when comparing bright colors of high chroma, if quick judgment cannot be got, the observer shall look at the neutral gray nearby for a few minutes before comparing; if the observer is making continuous comparison, a few minutes' break shall be constantly taken to ensure the quality of visual color comparison. Do not look at colorful items during a break.
(3) Size difference
Colors covering larger area look brighter and fresher than those covering smaller area, which is called the area effect. It is not appropriate to select object of large area based on the color sample of small area. In visual colorimetry, the test panel and the reference standard panel shall be flat with size not smaller than 120mm×50mm. (Qimao Application Elite Circle, the first We-media in the Industry)
(4) Background difference
Object in front of a bright background looks darker than that in front of a darker background, which is called the contrast effect. This is not adverse to determine a color accurately. During visual colorimetry, the judgment of observer will be affected by the surrounding colorful items. Therefore, the observer shall be in neutral color. In the field of view, no other colorful object than the test panel is allowed. While using light source, there shall be not reflected light of colorful items (e.g. red walls and green trees).
(5) Direction difference
When observing one object from two slightly different view angles, some point on the observed object may look different. This is because that color plane has directional characteristic.
3. Measurement and determination of colors
By establishing a scale for the three properties of color-color hue, brightness and chroma, we can use figures to measure a color. Currently, Munsell color system is internationally adopted. Other methods using figure to show colors are developed by International Commission on Illumination (CIE), among which there are two methods that are relatively famous, they are YXY color space method and L*a*b* color space method.
Symbols and meanings of the three properties in Munsell color system:
The symbol of color hue is H (hue) which means that the object is red, yellow, blue, purple or neutral color, one of the three properties of color.
The symbol of brightness is V (value), representing the reflected rays of an object, one of the three properties of color. The value of rational black is 0, white is 10, the perception difference on brightness from 0 to 10 is separated equally.
The symbol of chroma is C (Chroma)/saturation, representing the degree the color is away from the gray with the same value. Chroma is from 0 to 20, and a value lower than 0.5 often means no color.
II. Color mixing theory-based on the three-primary colors
Primary colors: magenta, yellow and cyan.
We can see colors because our eyes have perceptions of the light which is selectively absorbed by an object.
Secondary color: a color made by mixing two base colors with different ratios.
Compound color: a color made by mixing two secondary colors and other hues or different amounts of the three primary colors.
Complementary colors (complementary colors cannot be used at the same time in actual color mixing):
When two primary colors are mixed with different amounts to get a secondary color, the last primary color is its complementary color. When two secondary colors are mixed to form a compound color, the other corresponding secondary color is also its complementary color.
III. Attentions in color mixing process
1.Principles in color mixing
(1) Color retention
The lower the fading rate is, the better the color retention.
Being consistent with the color mixing theory based on three primary colors
(3) Contrast ratio
Covering rate (the rate covering base colors)
Contrast ratio and cost cannot be considered before the color retention meets requirements.
2.Method and basic requirements for color mixing
Although there are many varieties of monochrome color paste (also called original color paste), they cannot fully meet our needs. So we mix existing original color pastes to make more colors to meet users' demands.
Color mixing is complex and subtle, because there are so many kinds of colors and we need to know the performance of various colors and have precise judgment on the difference of colors.
In industrially developed countries, color measuring and color mixing instrument and computer programs are used for color mixing. The color and composition of test panel is analyzed through photoelectric spectrophotometer or spectrophotometer and recorded in figures. These figures are then input into program for color matching and mixing to calculate the ratio of all kinds of colors and the varieties of colors to reach the value index, which makes color mixing accurate and quick. In car repairing industry, computer color measurement and mixing system has been widely used.
The other method for compound color paint mixing is by manual, which is mainly based on actual experience. According to the color sample panel, the worker will recognize how many monochromes are there, and the rough ratio of each monochrome is determined. Then make sample mixing experiment and then make color mixing, all based on the basic principles of chromatics.