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2024-12-20
When measuring color, the colorimeter is based on the most widely used CIELab color space, and the color is expressed as Lab values. So, how do you understand the Lab value of a colorimeter? What is the standard for determining the Lab value of a colorimeter? This article introduces the meaning of the Lab value of a colorimeter and the standard for determining the Lab value.
Colorimeter Lab Value
The measurement principle of the colorimeter is based on the human eye's perception of color, namely the tristimulus method (RGB) and the symmetrical tristimulus method (CMY). The colorimeter contains a device called a light source and a device called a detector, which act as a transmitter and a receiver, respectively, to measure the reflectance spectrum of the sample.
The light source emits light of different wavelengths. After being reflected by the sample, the detector receives the reflected light and analyzes the intensity and wavelength of the reflected light to calculate the color value of the sample. When measuring, the sample should fit closely with the receiving head of the instrument to avoid the influence of stray light in the air and ensure accurate measurement.
The measurement results of a colorimeter are usually expressed in numerical values, including color coordinates, L*a*b* values, RGB values, etc. Among them, the L*a*b* standard is the color value representation method widely used in the industry. The L*a*b* values are used to describe the lightness (L*), red/green (a*), and yellow/blue (b*) components of any color, which are based on the CIE 1976 standard.
During the measurement process, the colorimeter will also compare with the measurement data of the known standard to evaluate whether the color of the sample meets the standard requirements and determine the difference between the sample and the standard. This comparison method is called color difference analysis and is often used in quality control and quality management to ensure that the color and appearance of various products are consistent and stable.
In short, the colorimeter is a high-precision measuring tool whose measurement principle is based on the human eye's perception of color. It is used to measure and analyze color differences and is an important tool for color control and quality management in modern industrial production.
Colorimeter Lab Value
L, a, a on the colorimeter are the chromaticity values representing the color of the object, that is, the color space coordinates of the color. Any color has a unique coordinate value, where L represents lightness (black and white), a represents red and green, and a represents yellow and blue. When using a colorimeter, three sets of data, L, a, and b, and four sets of color difference data, △E, △L, △a, and △b, are generally output. The size of the total color difference of △E, △L+ means brighter, △L- means darker, △a+ means redder, △a- means greener, △b+ means yellower, and △b- means bluish.
The Lab color model is composed of three elements: illumination and a and b, which are related to color. L represents illumination, which is equivalent to brightness, a represents the range from magenta to green, and b represents the range from yellow to blue. The value range of L is from 0 to 100, and when L=50, it is equivalent to 50% black. The value ranges of a and b are both from +127 to -128, where +127a means that magenta gradually transitions to -128a and then turns into green; in the same principle, +127b is yellow and -128b is blue. All colors are composed of these three values that change alternately.
Colorimeter Lab Value Determination Standard
A colorimeter is an instrument used to measure the color of an object. In a laboratory, the colorimeter Lab judgment standard is very important. Through the colorimeter Lab judgment standard, the color difference of an object can be accurately evaluated, which is critical for color quality control and product consistency. The following will introduce the relevant content of the colorimeter Lab judgment standard in detail.
First of all, the colorimeter Lab judgment standard is based on the CIELab color space. The CIELab color space is a universal color space that can describe all colors perceived by human vision. In the CIELab color space, L represents brightness, a represents red and green components, and b represents yellow and blue components. The colorimeter Lab judgment standard evaluates the color of the sample by measuring the Lab value of the sample.
Secondly, the △E value in the colorimeter Lab judgment standard is an important indicator for measuring color differences. The △E value indicates the distance between two colors in the CIELab color space, that is, the degree of color difference. Generally speaking, a △E value less than 1 means that the colors are almost indistinguishable, a △E value between 1 and 2 means that the color difference is slight, and a △E value greater than 2 means that the color difference is obvious. By comparing the △E value of the sample with the standard value, it can be determined whether the color of the sample meets the requirements.
In addition, the colorimeter Lab judgment standard also includes the selection of color difference formulas. Commonly used color difference formulas include CIE1976 Lab color difference formula (△Eab), CIE1994 Lab color difference formula (△E94), CIE 2000 Lab color difference formula (△E00), etc. Different color difference formulas have different ways of calculating color differences. Choosing a suitable color difference formula can more accurately evaluate color differences.
Finally, the Lab judgment standard of the colorimeter needs to pay attention to the control of measurement conditions. When measuring color, it is necessary to control the consistency of factors such as light source, observation angle, and measurement conditions to ensure the accuracy and repeatability of the measurement results. In addition, factors such as the surface quality of the sample and the color environment will also affect the color measurement results, which need to be considered and controlled during the experiment.
In summary, the colorimeter Lab judgment standard is based on the CIE Lab color space, and the color difference is evaluated by measuring the Lab value and △E value of the sample. Selecting the appropriate color difference formula and controlling the measurement conditions are the key to ensuring the accuracy of color difference measurement. In practical applications, it is necessary to strictly follow the colorimeter Lab judgment standard for color measurement and evaluation to ensure the consistency of product color and the stability of quality.
The △E*ab formula in the colorimeter is a mathematical formula used to calculate the color difference between two colors. △E*ab is a color difference metric defined by CIE (International Commission on Illumination) to measure the perceived difference between two colors in the human eye. The formula is based on the CIE1976Lab color space, where L represents brightness, a represents the axis from red to green, and b represents the axis from yellow to blue.
The calculation formula of △E*ab is as follows:
△E*ab= [(△L*)2 +(△a*)2 +(△b*)2]1/2
Among them, △L represents the brightness difference between two colors, △a represents the red-green difference between two colors, and △b represents the yellow-blue difference between two colors. This formula calculates the difference between these three color components to get an overall color difference value.
The application of this formula can help people evaluate and compare the degree of difference between different colors, which is very useful for color matching and quality control. In industrial production, colorimeter is often used to detect the color consistency of products, such as textiles, coatings, plastic products, etc. In addition, the food industry also uses colorimeter to detect whether the color of food meets the standard.
In general, the △Eab formula is an important formula used in colorimeter to calculate the color difference between two colors. It is widely used in industrial production and scientific research.
