HueSense

Color Discrimination in Design and Print — Tolerances and Quality Checks

How ΔE is used to set color tolerances in brand color management, print proofing and textile and paint color matching, plus the standard light sources, viewing conditions and tests used to compare colors in practice.

In jobs that deal with color, color discrimination is quality. But in practice nobody relies on one person's eyes alone. ΔE measured with an instrument and visual inspection under standard conditions are used together.

A tolerance is a number in a contract

When delivering brand colors, printed materials, coatings or textiles, parties usually agree that the color difference between the reference sample and the delivered product must be within a certain ΔE. There is no single right number. It is agreed between the parties based on the product, its use, price and process capability.

In practice, roughly ΔE00 1–2 is often treated as a strict tolerance and 2–3 or more as a loose one, but that is only convention. What matters is always stating the following three things together.

Print: proofing and standard conditions

In the print industry, the colors of proofs and production runs are measured with a spectrophotometer and compared by eye in a standard-condition viewing booth. Graphic arts use the D50 illuminant as the reference, and ISO 3664 specifies the lighting conditions for comparing prints. For soft proofing, where print output is previewed on screen, the monitor is calibrated and the same conditions are matched.

Textiles and coatings: watch out for metamerism

Fabrics and paints often match the same color using different combinations of dyes or pigments. In that case, two samples that look identical under one light can look different under another; this is called metamerism. That is why samples are compared in a viewing booth under several light sources, such as daylight (D65), store lighting and incandescent light (A). The textile industry has long used the CMC(2:1) formula, which is more lenient on lightness differences.

Digital design: every screen shows color differently

In web and app design, a color that looks right on one screen looking different on another is an everyday occurrence. When defining colors in a design system, specify the color space (sRGB, Display P3) along with the color values, and build palettes in clearly distinguishable steps so you do not end up with several near-identical colors. If the ΔE00 between two adjacent colors is too small, users see them as the same color and the meaning is lost.

It is also important not to convey information through color alone. Use lightness contrast, icons and text as well, so the information reaches users with color vision deficiencies and those on low-quality screens.

How human color vision is tested

Standardized color arrangement tests are used in hiring and training for color-critical roles. The best known is the Farnsworth-Munsell 100 Hue test, in which caps with slightly different hues are arranged in order, and color discrimination is assessed from how much and in which direction the arrangement is off. It is only meaningful when administered under standard lighting following the prescribed procedure.

Screen tests like HueSense cannot replace such tests. They are useful, however, for getting a quick sense of your weak directions and for building up a practice record by repeating the test under the same conditions.

References

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