When you transform three stimulus values XYZ into UCS(Uniform Color Space), it can be displayed at L*a*b* Color Specification System, Three-Dimentional Sphere (See Figure.10) and you can compare small and large of perceptual color difference in the distance of two colors coordinates.
In other words, the range of color allowance is expressed by color difference value.
Basically, the color allowance should be judged by agreement between the parties. For your reference, See Figure.11. In this figures, we introduce the case in common use at ISO regulation or in a variety of industries.
[Figure.11 : Example of Allowance by Color]
Color Tolerance |
Color difference ΔE* |
The extent of color difference |
Standards |
Avaluative level |
0～0.2 |
The extent that Human can't discriminate. It is impossible to measure the color differences using the special adjusted measuring instruments. |
|
The limit of discrimination |
0.2～0.4 |
It is possible to measure the color differences in the range of 0.2 ～ 0.4, using the special adjusted measuring instruments. The people who was trained can distinguuish. |
ISO 105-A02 ISO 105-A03 |
Grade AAA Color tolerance |
0.4～0.8 |
This is the limit to set up the strict color difference standards with the decision of the human visual. |
The particular strict standards stipulated between the persons concerned |
Grade AA Color tolerance |
0.8～1.6 |
People can tell the color differences, if samples are put side by side. |
The standard of the Defense Agency. The standard of the National Police Agency. The standard of general ship inspection. |
Grade A Color tolerance |
1.6～3.2 |
In color comparison, this level is regarded as unrecognized and same color in general. |
The color tolerance of general color chips. |
Grade B Color tolerance |
3.2～6.5 |
Each colors of this range are regarded as the same colors. But the clients concerning paints and inks industry will make complaints about the color difference. |
The allowable color difference in color management in general. |
Grade C Color tolerance |
6.5～13.0 |
This color tolerance corresponds to the color difference of JIS standard color chips. |
ISO 9177-3 |
Grade D Color tolerance |
13.0～25.0 |
Each colors over ΔE 13 are not same color anymore. |
ISO 3864-1 |
