Observer angle 2° vs 10°
The colorimetric observer is one of the parameters that affect a colour reading. We explain the difference between the 2° and 10° observers and how to choose.
What the colorimetric observer is
To convert a spectrum into colour coordinates you need a model of the human eye’s response — the CIE standard observer. Two are defined: 2° (CIE 1931) and 10° (CIE 1964). The number is the angular field of view of the sample for which the colour-matching functions were derived.
- The 2° observer covers a narrow, central field of view (the fovea). It corresponds to viewing a small object from a greater distance.
- The 10° observer covers a wider field of view and better reproduces the assessment of larger surfaces up close — which is why it is more often recommended in industry today.
Which to choose
The key rule: always measure the standard and the sample with the same observer. Results for 2° and 10° differ and must not be mixed. In practice:
- 10° — the default choice for most industrial applications assessing larger surfaces (textiles, plastics, paints, coatings).
- 2° — when required by a standard, a customer specification, or when small details are assessed.
All 3nh spectrophotometers and colorimeters support both observers — just set the same one as the standard. As with geometry and illuminant, consistency of settings matters more than the choice itself.
Frequently asked questions
Observer 2° or 10° — which is better?
Neither is "better" — they suit different viewing conditions. Industry more often uses 10° because it better reproduces the assessment of larger surfaces. The most important thing is to measure the standard and the sample with the same observer.
Can I compare a 2° result with a 10° result?
No. Colour coordinates and ΔE depend on the observer, so 2° and 10° values are not comparable. Always set the same observer for the standard and the sample.
How do I choose the observer for my quality control?
Check what your standard or customer specification requires. If neither dictates the choice, we recommend 10° for typical industrial surfaces. We are happy to help you set it up correctly.