ColorAptitude™

ColorAptitude™ was developed in accordance with the guidelines of ASTM E1499-16 and uses established colorimetric standards. Below you will find an explanation per standard.

ASTM E1499-16

Standard Guide for Selection, Evaluation, and Training of Observers

ASTM International, West Conshohocken, PA (2016)

The design framework for the entire platform. ASTM E1499-16 describes how visual assessors should be selected, evaluated and trained in colour-critical industries.

Section	Subject
§5.3	Warning against uncalibrated replicas of physical tests.
§6.3.2	Triangle Test — basis for the chroma threshold assessment.
§6.4	Magnitude Scaling — estimation of colour difference magnitude on a ratio scale.
§7.1.1	Warmup — requirement of a practice period before assessment.
§8.1.1	Session limits — maximum duration of a test session.

Application in ColorAptitude™: ColorAptitude™ follows the ASTM E1499 structure for warmup, session limits, and test setup. The platform is not a replica of a physical test (§5.3), but an independent digital qualification instrument that implements the guidelines from the standard.

Farnsworth-Munsell 100 Hue Test

FM100 Hue Arrangement Test

Farnsworth, D. (1957); Munsell Color Company

The gold standard for measuring colour discrimination ability via cap ordering. 85 colour caps are arranged in four trays in order of hue.

Application in ColorAptitude™: The error formula for the Hue Ordering Diagnostic is based on the FM100 method. For each cap the absolute difference is calculated between the positions of the neighbours and the placed position. The Total Error Score (TES) is normed via √TES transformation according to Kinnear & Sahraie (2002).

CIEDE2000

CIE DE2000 Color-Difference Formula (Sharma, Wu & Dalal, 2005)

Commission Internationale de l'Éclairage (CIE)

The most accurate formula for measuring perceived colour differences. CIEDE2000 corrects for non-uniformities in earlier formulas (CIE76, CIE94) and applies weighting factors for lightness, chroma and hue.

Application in ColorAptitude™: All inter-stimulus distances in ColorAptitude™ are computed in OKLCH perceptual space (Ottosson, 2020). CIEDE2000 (ΔE₀₀) is referenced for cross-comparison with industry partners that report deviations in that metric, but it is not the basis of the ColorAptitude scoring pipeline.

OKLCH (Oklab LCH)

Perceptually uniform colour space (Ottosson, 2020)

Björn Ottosson

A modern perceptually uniform colour space that separates lightness (L), chroma (C) and hue (H) in a cylindrical coordinate system. Unlike HSL/HSB, OKLCH offers consistent perceptual steps across the full colour spectrum.

Application in ColorAptitude™: All stimuli in ColorAptitude™ are generated in OKLCH space. This guarantees that a step in chroma looks perceptually equal for blue as for yellow, and that hue transitions are perceptually uniform.

CIE 2006 Standard Observer

CIE 170-1:2006 Fundamental Chromaticity Diagram with Physiological Axes

Commission Internationale de l'Éclairage (CIE)

The reference model for human colour perception based on physiological cone responses (LMS cone functions). Replaces the CIE 1931/1964 functions with spectral sensitivity curves closer to the actual cone response.

Application in ColorAptitude™: The platform uses the CIE 2006 observer as reference to contextualise individual deviations (due to lens yellowing, age, or genetic variation in cone density). Shi et al. (2023) showed that individual CMFs can deviate significantly from the standard.

Overview: which standard supports which assessment?