The color difference meter is a precision optical measuring instrument that accurately measures the color difference through the principle of light/electricity conversion. Generally, the color data of the measured object is collected from five angles (15°, 45°, 110°), and the measurement results are obtained by analyzing and comparing the collected standard sample data and the sample data.
In the field of optics, color can be measured by the Lab color scalar, the L-axis is the brightness axis, 0 is black, 100 is white; A-axis is red and green axis, positive value is red, negative value is green, 0 is neutral color; The b axis is a yellow and blue axis, positive values are yellow, negative values are blue, and 0 is a neutral color. These scales can be used to represent the color difference between the sample and the standard sample, usually Δa, Δb, ΔL as the identifier, ΔE is defined as the total color difference of the sample, but it cannot represent the deviation direction of the sample color difference, the larger the value of ΔE, the greater the color difference. According to the Lab and Lch principles of CIE chromaticity space, the color difference ΔE, Δa, Δb, ΔL values between the sample and the standard sample can be measured and displayed.
ΔE is usually calculated by the following formula:
Δ E * = [(Δ L *) + (Δ a *) + (Δ b *)] 1/2
Sometimes some companies will require a total color difference of less than 2, and some will also require a Lab value. If ΔE≤2.0, it is recommended that Δa, Δb, ΔL are all ≤1.5, and it is generally distinguishable visually when ΔE is 1.5. Since Δa, Δb, ΔL are generally not fixed, in the case of too strict requirements, often on the total color difference ΔE and color difference Δc (without considering the brightness effect) have requirements, at this time can be calculated according to the following formula:
ΔE*=[(ΔL*)+(Δa*)+(Δb*)]1/2 Δc*=[(Δa*)+(Δb*)]1/2
The color difference meter is based on the Lab, Lch principle of CIE color space, the measurement shows the color difference △E and △Lab value of the sample and the sample to be measured. The product is widely used in the color detection of paint, ink, textile, clothing, leather, plastic, plastic, printing, coating, metal, etc., then what does the l ab on the color difference meter represent?
L: black and white, also said light dark, + means white, - means dark;
A: indicates red green, + indicates red, - indicates green;
B: indicates yellow and blue, + indicates yellow, - indicates blue;
The above are relative values, simple L,A,B is absolute value, with these three values can be in a three-dimensional map, accurately represent a color point, with the relative value can be obtained and the reference point difference to correct the total color difference ΔΕ= (Δa2+Δb2+Δl2) 1/2.
CIE (International Commission on Lighting) Lab Color Space Brief introduction:
L:(Brightness) axis represents black and white, 0 is black and 100 is 100
a:(red green) Positive values are red, negative values are green, and 0 is neutral.
b; (yellow blue) axis positive values are yellow, negative values are blue, and 0 is neutral.
All colors can be perceived and measured through the Lab color space, and these data can also be used to represent the color difference between the standard sample and the test sample, and are usually expressed as △Eab (total color difference) △L △a △b.
For example, △L is positive, indicating that the test sample is lighter than the standard sample (white) △L is negative, indicating that the test sample is darker than the standard sample (black).
For example: △a is positive, indicating that the test sample is more red than the standard sample (red) △a is negative, indicating that the test sample is more green than the standard sample (green)
For example: △b is positive, indicating that the test sample is more yellow than the standard sample (yellow) △b is negative, indicating that the test sample is more blue than the standard sample (blue)
△Eab(or △E) is the total color difference, it does not indicate the direction of the color difference shift, the greater the value indicates the greater the color difference.