How to measure color difference? What are the methods of measuring

Color difference measurement is a crucial part of color management, involving aspects such as color accuracy, product quality control, and color standard formulation. How is color difference measured? What are the methods for measuring color difference? This article provides a simple summary.

Basic Principles of Color Difference Measurement

Color difference measurement is based on the human eye's visual perception of color. It evaluates color differences by comparing the color differences between a sample and a standard color card or standard color sample. Color difference is usually expressed by a numerical value. The smaller this value is, the smaller the color difference is, and the higher the color accuracy is. The basic principles of color difference measurement include the selection of color space, the establishment of color models, and the calculation of color difference formulas.

Methods for Measuring Color Difference

Visual Evaluation Method

The visual evaluation method is the simplest and most direct way to measure color difference. It relies on the human eye's visual perception and evaluates color differences by comparing the color differences between a sample and a standard color card or standard color sample. This method is simple and easy to implement, requiring no complex equipment or technology. However, it has high requirements for the evaluator's experience. The drawback of the visual evaluation method is its strong subjectivity, which is easily affected by factors such as ambient light and viewing angle, resulting in unstable evaluation results.

Instrument Measurement Method

The instrument measurement method is a way to evaluate color difference using professional color difference measurement instruments. This method has high accuracy and objectivity, and can eliminate the subjectivity and uncertainty of human eye evaluation. Common color difference measurement instruments include spectrophotometers, chromatographs, and color measuring instruments. The instrument measurement method is suitable for color difference evaluation occasions that require high precision and stability, such as the printing, coating, and textile industries.

Selection of Color Difference Measurement Instruments

Color difference measurement instruments are key equipment for color difference measurement. Choosing the right instrument is crucial for ensuring measurement accuracy. When selecting a color difference measurement instrument, the following aspects need to be considered:

Measurement Range: Ensure that the instrument can cover the required color measurement range.

Accuracy and Stability: Accuracy and stability are important indicators for measuring instrument performance. Instruments with excellent performance need to be selected.

Ease of Operation: The operation of the instrument should be simple and easy to understand, facilitating user use.

Price Factor: Select an instrument with a high cost - performance ratio according to actual needs.

Method Steps for Measuring Color Difference with a Colorimeter

Preparation Work: Before measuring color difference, ensure that the sample surface is clean and free of flaws, and prepare a standard color card or standard color sample.

Instrument Calibration: Perform calibration operations according to the instrument manual to ensure that the instrument is in the best working condition.

Measurement Steps: Place the instrument in a stable measurement environment and measure the sample and the standard color card or standard color sample. Pay attention to maintaining the consistency of measurement conditions, such as light source and viewing angle.

Data Processing: Input the measured data into the corresponding software and use the color difference formula for calculation to obtain the color difference value.

Common Problems in Color Difference Measurement and Solutions

Instrument Error: Regularly calibrate and maintain the instrument to reduce the impact of instrument error on the measurement results.

Inconsistent Measurement Conditions: Ensure a stable measurement environment and avoid interference from factors such as light source and viewing angle on the measurement results.

Sample Surface Problems: Ensure that the sample surface is clean and free of flaws to avoid the impact of surface problems on the measurement results.

Operation Error: Familiarize yourself with the instrument operation method and follow the measurement steps to reduce operation errors.

Color difference formulas are mathematical formulas proposed to quantify the difference between two colors. In color matching and quality control, color difference formulas are widely used to measure and compare the similarity of colors. So, how are color difference formulas calculated? This article briefly introduces the calculation method of the common color difference formula ΔE*.

Color Difference Calculation Formula

Color difference is a quantitative indicator used to measure the degree of difference between two or more colors. In color difference calculation, the CIE Lab* color space is usually used as a standard. This color space encompasses all possible colors, making it easier to compare different colors.

In the CIE Lab color space, L represents the lightness of the color, a represents the axis from green to red, and b represents the axis from blue to yellow. The color difference calculation formula is usually expressed by △E, and its calculation formula is as follows:

△E = [(△L*)² + (△a*)² + (△b*)²]^0.5

where △L*, △a*, and △b represent the differences of the two colors on the L, a, and b axes respectively. The significance of this formula is to combine the differences of the two colors in three dimensions into a single value, thus obtaining a single number for describing the degree of color difference.

Calculation Method of the Color Difference Formula ΔE*

A color difference meter is a common tool for calculating the color difference formula ΔE*. The principle of a color difference meter is based on optical principles, that is, color is composed of the wavelength and intensity of light. The color difference meter calculates the difference between colors by measuring three main parameters of color: lightness, saturation, and hue.

A color difference meter is a tool for measuring the difference between colors. Its calculation formula uses the CIE Lab* color space and calculates the difference between colors by measuring parameters such as the lightness, saturation, and hue of colors. The principle of a color difference meter is based on the fact that the human eye has different sensitivities to different colors, and that color can be represented as a combination of three basic parameters: lightness (L*), green - red hue (a*), and blue - yellow hue (b*). These parameters combine to form the CIE Lab* color space, which plays a key role in color difference calculation.

The working principle of a color difference meter is to measure the reference sample and the test sample respectively, and convert their color parameters into values in the CIE Lab color space. Then, it calculates the differences of the two samples in the L, a, and b parameters, that is, the color difference. There are several commonly used color difference calculation formulas, among which the most commonly used is the ΔE*ab formula, also known as the CIE 1976 color difference formula. Its calculation method is:

ΔEab = [(ΔL)² + (Δa*)² + (Δb*)²]^0.5

where ΔL*, Δa, and Δb are the differences in the L*, a, and b parameters between the test sample and the reference sample respectively. The smaller ΔE*ab is, the smaller the difference between the two colors is; conversely, the larger it is, the greater the difference.

In addition to the ΔE*ab formula, there are other color difference calculation formulas, such as CIEDE2000, CIELUV, etc. Different formulas are applicable to different color measurement requirements. In practical applications, choosing a suitable formula can more accurately measure the difference between colors.

The calculation formula and principle of a color difference meter are based on the CIE Lab* color space. It calculates the difference between colors by measuring color parameters, thus playing an important role in color management and quality control.

In addition to the CIE Delta E formula, there are many other color difference formulas, such as CIE94, CIEDE2000, etc. These formulas differ in calculation methods and application scenarios, but the basic principle is to calculate based on the RGB values or Lab values of colors. In practical applications, it is necessary to select an appropriate color difference formula according to specific needs and scenarios for color matching and quality control.

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