Choosing Color Deviation Tolerances

Quantifying Colors

Colors are generally defined by their position in the Lab color space, which is a 3D color model representing all colors visible to the average human eye (developed by the Commission Internationale de l'Eclairage).

It is based on three axes:





For example:

Color

Lab values

light yellow

Lab (100, 0, 60)

dark green

Lab (15, -128, 0)

medium grey

Lab (50, 0, 0)

Difference Between Colors: Delta E

The difference between two colors is the difference between their respective positions on the L, a and b axes. This difference is called the Delta E (or ), and is calculated using a mathematical formula.





The more different two colors are, the higher the Delta E number is. Generally a human eye can perceive color differences that are above 2 Delta E.

Note:

There are several Delta E formulas, that have been developed at different points in time (CIE76, CMC, CIE94 and CIE2000).

  • If your company is already using one of those formulas, we recommend that you use the same one.
  • If not, you should use the most recent one, CIE2000, which is the best reflection of the visual difference between colors.
  • However, if you are trying to verify your proof according to the ISO 12647-7 proofing standard, you should use the formula specified in the standard, CIE76.

Difference Between Colors: Other Measures

Apart from Delta E, there are additional color differences indicators, that measure other colors characteristics.

You can use those if you want to have a more comprehensive picture of how well your colors are reproduced, or to quantify a particular color problem of your press.

Delta F

Use this to measure the difference in saturation (or "chroma") between the colors in your job and the printed colors.

This is based on the positions of the two colors on the a and b axes in the Lab color space, and can be a good indication of whether the gray balance on your press is good or not.

Delta H

Use this to measure the difference in hue between the colors in your job and the printed colors.

The hue is the angle between two colors relative to the a and b axes in the Lab color space.





Delta T

Use this to measure the difference in colorimetric tone value between the colors.

Colorimetric tone value means that the dot gain is measured by a spectrophotometer instead of a densitometer.

This gives more information about the colors (for example 50% of a warm yellow and 50% of a cold yellow look the same to a densitometer, but different to a spectrophotometer).

This is only applicable to the primary colors (CMYK).

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