Definition
Inter-rater variation (inter-observer variability) is the natural difference in colour perception and assessment between individual assessors. Even with a standardised setup (fixed illumination, viewing angle, background), two persons can measurably assess the same colour sample differently.
Background
Major causes of inter-observer variability are:
- Physiological: density and ratio of cone cells differs per individual, as does the yellowing of the eye lens (increases with age)
- Perceptual: chromatic adaptation and colour constancy vary; the visual system compensates environmental conditions differently per person
- Cognitive: experience, training and attention influence how colour information is processed and reported
- Environmental factors: even small deviations in illumination or viewing angle — which can vary per assessment — amplify the spread
Research (Hita et al., 2001; Kirchner et al., 2015) shows that inter-rater variation is in the order of ΔE00 1.0–3.0 for trained assessors, and up to ΔE00 5.0+ for untrained persons.
Relevance to ColorAptitude™
ColorAptitude™ quantifies inter-rater variation directly: each user receives an individual colour profile that shows where their perception deviates from the average. By having teams test, the spread within a group becomes objectively measurable.
This is crucial for organisations that work according to ASTM E1499-16: the standard prescribes that the mutual variation of assessors must be within acceptable limits. ColorAptitude™ makes this visible and offers targeted training to reduce the variation.