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What does the Lab value on the color difference meter mean

Source: Colorimeter Browse: Release date: 2018-05-25

What does the Lab value on the color difference meter mean

L means black and white, but also light and dark, + means whiter,-means darker

A means red and green, + means reddish, and-means greenish

B means yellowish blue, + means yellowish,-means blueish

In the process of using the color difference meter, the most we analyze is the Lab value. The color difference and Lab are closely related, so we must learn Lab and LCH first to understand and handle the color difference. First of all, let's take a look at the CIE Lab color space. Here is a brief explanation, L represents black and white, a represents red and green, and b represents yellow and blue. The following figure shows the changes of L, a, and b in Lab.

LCH is the same chromaticity space as Lab, except that in LCH, L represents the lightness value; C represents the saturation value and H represents the hue angle. Many color difference meters now support the LCH color detection standard. The following figure shows the relationship between Lab and LCH.

All colors can be perceived and measured through the Lab color space. These data can also be used to indicate 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 (whiter) than the standard sample; △ L is negative, indicating that the test sample is deeper (blacker) than the standard sample

For example: △ a is positive, indicating that the test sample is red (reddish) than the standard sample. △ a is negative, indicating that the test sample is greener (greenish) than the standard sample.

For example: △ b is positive, indicating that the test sample is yellower than the standard (yellowish). △ b is negative, indicating that the test sample is bluer than the standard (blueish).

△ Eab (or △ E) is the total color difference. It does not indicate the direction of the color difference shift. The larger the value, the larger the color difference.

2 +( a) 2 +( b) 2 △ E is the comprehensive evaluation index of color difference, and its relationship with △ L, △ a, △ b is: E = ( L) 2 + ( a) 2 + ( b) 2

Color difference Delta E * (△ E)

According to the actual situation and the numerical calculation results of the color difference calculation formula, the following conclusions can be drawn:

△ E is between 0-1, the color difference is indistinguishable to the naked eye

△ E is between 1-2 and can be slightly detected by the naked eye

△ E is between 2-3, can clearly distinguish the color difference between substances

△ E is between 3.5-5, the color difference is very obvious

△ E is more than 5, then it is a very large color difference, and it even looks like two colors.



Color difference meter to test Lab values of different foods

Tested sample L * a * b * E Sensory evaluation
Salty Toast Cuticle 46.66 +16.80 +26.27 +25.45 Uniform brown
Internal salty toast 81.34 -0.45 +18.75 +55.16 White, delicate, uniform honeycomb organizational structure
Sweet toast epidermis 51.08 +17.36 +29.72 31.02 Even tan, slightly darker than salty toast
Sweet toast interior 82.60 -0.33 +18.62 56.29 White and delicate honeycomb structure
corn starch 101.69 +0.37 +4.03 6.39 Whiter than white
Potato starch 99.27 +0.31 +2.64 5.67 Close to standard board whiteness
Flour 1 95.84 +0.92 +7.46 0.83 Whiteness is close to standard color
Flour 2 94.88 +0.79 +11.20 4.51 The whiteness is close to the standard color, showing a slight cream yellow
表皮 Northern Steamed Bun 1 Epidermis 90.23 +0.28 +13.11 13.52 Hoe epidermis
表皮 Northern Steamed Bun 2 Epidermis 91.16 -0.45 +13.32 13.25 偏白亮中呈轻微乳黄色 The epidermis of the steamed bun is slightly whiter and brighter than 1
Southern steamed bun epidermis 64.36 -0.47 +12.14 3.48 Pure and bright
Southern steamed bun inside 94.36 -0.87 +12.10 5.26 Delicate white compact organizational structure
Soy flour Lot 1 83.83 -0.59 +25.56 59.25 Receiving a sample of normal
Soy flour batch 2 86.01 -3.28 +25.24 61.25 色泽稍暗,当尚可接受 Slightly darker than batch 1 , acceptable when
Banana paste (without fruit filling) 75.89 -4.43 +70.46 66.89 Glossy and bright banana characteristic yellow
Apple filling (including fruit filling) 59.45 -2.89 +33.64 43.55 Light tan
Mango filling (including fruit filling) 90.47 1.64 +53.77 47.22 Mango has glittering feeling characteristic bright yellow

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