CIELAB
CIELAB is a color space used for color difference management by quantifying color with L* for lightness, a* for the red-green axis, and b* for the yellow-blue axis.
Contents6 sections
Definition and Overview
CIELAB is one of the color systems defined by the International Commission on Illumination. It expresses color with three coordinates, L*, a*, and b*, and is used to share color differences numerically that are difficult to convey by eye. It is not a type of fabric itself, a weave structure, or a processing name.
L* indicates lightness, and the larger the value, the lighter the color. a* is the axis for red and green tendencies, and b* is the axis for yellow and blue tendencies. By combining the three values, the position of a color can be managed in a three-dimensional way.
- L*: an index of lightness.
- a*: the positive side indicates red, and the negative side indicates green.
- b*: the positive side indicates yellow, and the negative side indicates blue.
How Color Appears and Quality Control
CIELAB values do not directly indicate hand feel, shrinkage, washability, or sewability. On the other hand, they are useful as a common language for checking differences in hue, lightness, and saturation in dyeing and printing, and for bringing them closer to the sample color.
Even when the Lab values are close, the appearance changes depending on the light source, viewing direction, surface gloss, fuzz, and structure. In particular, metamerism, where colors look different depending on the light source, cannot be judged by numbers alone, so visual confirmation under the specified light source is also necessary.
Main Uses
In apparel, it is used for lab dips, strike-offs, color matching for mass-produced rolls, and color checks of printed patterns. It is used in situations where color control is needed against brand standard colors or advance samples, regardless of season or item.
Color difference is generally expressed as ΔE and calculated from the Lab values of the standard color and the sample. In purchase orders and inspection standards, it is easier to reduce differences in understanding between trading partners if the measuring conditions, acceptable color difference, and judgment method are decided in advance.
Points to Note in Operation
When comparing color measurement values, it is important to align the measuring device, light source, observer conditions, sample layering, and the direction of the measuring surface. For brushed items, glossy items, heathered items, and thin sheerness items, also check variation in values depending on the measuring location.
Discoloration and color change caused by washing, friction, sunlight, and heat cannot be evaluated by the initial Lab values alone. Check color difference before and after fastness tests appropriate to the application, and set standards suitable for care labels and the wearing environment.
In sewing, check the colors of the outer fabric, accessories, and sewing thread separately. Even with the same color number, differences in material or gloss may make the colors appear not to match. Assume the lighting environment of the finished product and check both before cutting and after sewing.
Differences from Similar Terms
ΔE is a color difference that numerically shows the distance between two colors. While CIELAB is the coordinate system used to express color, ΔE is used to evaluate the color difference based on those coordinates.
A grayscale is a sample mainly used to visually judge the degree of discoloration and staining. Lab values are numerical color management by measurement, while a grayscale is a visual comparison with a standard sample.
Frequently Asked Questions
Can fabric color be determined using only Lab values?
Lab values are useful for color management, but they cannot be used alone for the final decision. Fabric gloss, fuzz, unevenness, and sheerness affect how it looks. It is important to place the sample and the actual item side by side under the specified light source and viewing conditions, and use both visual evaluation and color measurement values.
What is the difference between CIELAB and ΔE?
CIELAB is a color space for expressing color with L*, a*, and b*. ΔE is an index of color difference obtained by comparing the Lab values of the standard color and the sample. In other words, CIELAB shows the coordinates of color, and ΔE shows the distance between two colors.
Can color changes after washing also be managed with Lab values?
Yes, they can. Measure the same areas before and after washing under the same conditions, and check the changes in Lab values and ΔE. However, evaluating practicality also requires test results such as wash fastness, appearance changes, and checks for staining on white areas.
