In the actual production process, when a product is composed of multiple parts and components, which are supplied by multiple suppliers, and we require the overall appearance color of the product to be consistent, we will encounter the problem of chromatic aberration of product appearance paint color .
What to do after encountering the product appearance paint chromatic aberration problem?
How can we assess whether the product color provided by the supplier meets our requirements?
How many colors are there?
Human eyes distinguish colors according to the wavelength of visible light, and colors vary with different wavelengths (like the rainbow).
In the spectrum, most colors can be mixed with red, green, and blue in different proportions.
Therefore, color can be represented by RGB value.
On the computer, we use bytes (1byte=8bit) to represent the color component.
When converted to decimal, one byte can represent 256 colors.
The color represented by RGB is R (0-255), G (0-255), B (0-255) and RGB can express 256 × 256 × 256 = 16777216 colors.
In addition to the commonly used RGB color representation, there is also the HSV color space: hue (H), saturation (S), lightness (V).
The range of hue (H) values is 0°~360°, and the range of saturation (S) and lightness (V) values is 0-1.
In addition to the above two color representation methods, there is also the Lab color space representation method.
The laboratory's color space is based on the perception of colors by human eyes and can represent all the colors that human eyes can sense.
The Lab color space can compensate for the uneven color distribution of the RGB color model and is the color representation mode that currently covers the widest color gamut.
L: represents light and dark (black and white), △L large indicates partial white, △L small indicates partial black;
a: represents red and green, △a large one indicates partial red, △a small one indicates partial green;
b: represents yellow and blue, large △b indicates yellowish and small △b indicates bluish;
Additionally, the Lab color space also defines the color difference valueΔE.
The color difference value is used to represent the color difference.
ΔE=0~0.5 extremely small difference, which can hardly be determined with the naked eye;
ΔE = 0.5 ~ 1.0 small difference, which is the allowable range of general color difference;
ΔE=1.0~1.5 small difference, acceptable in specific applications;
ΔE=1.5~3.0 the difference in the degree of perception with the naked eye is acceptable in specific applications;
ΔE=3.0~6.0, a very significant difference.
How to check the paint color difference from product appearance? What are the criteria?
In product drawings, paint color requirements generally use the color number of the color card provided by the manufacturer to indicate the specific paint color, commonly used are ral color card and Panton color card.
In paint color inspection, we generally use standard color plates to evaluate whether the color can meet our requirements through sensory comparison.
When using color panel comparison, we can only judge whether the colors are consistent, but we cannot provide accurate color difference information to the supplier.
Therefore, to quantify the difference between the paint color and the color we need, we need to use a color difference meter to judge.
The laboratory value, △L, △a, △b,ΔE value of the paint can be read quickly using the color difference meter.
The following is the meaning of color difference.
For a comprehensive color difference valueΔE, the general acceptance requirement is less than 0.5. If the requirement is not strict, ΔE can be relaxed accordingly.
| Chromatic aberration value | <-4 | -4~0.2 | -0.2~0.2 | 0.2~4.0 | >4.0 |
| △L | black and white | A little black and less white | normal | A little white and a little black | black and white |
| △a | Red-green deficiency | A little green and less red | normal | A little red and less green | Red and green |
| △b | Bluish and yellowish | Slightly blue and less yellow | normal | Slightly yellow and less blue | Yellowish and bluish |
