Measuring Instruments

Giving Shape to Ideas

Precise Color Communication

The color sensitivity of the eye changes according to the angle of view (object size). The CIE originally defined the standard observer in 1931 using a 2 field of view, hence the name 2 Standard Observer. In 1964, the CIE defined an additional standard observer, this time based upon a 10 field of view; this is referred to as the 10 Supplementary Standard Observer. To give an idea of what a 2 field of view is like compared to a 10 field of view, at a viewing distance of 50cm a 2 field of view would be a 1.7cm circle while a 10ذ field of view at the same distance would be an 8.8cm circle. Most of the information in this booklet is based on the 2ذ Standard Observer. The 2 Standard Observer should be used for viewing angles of 1 to 4; the 10 Supplementary Standard Observer should be used for viewing angles of more than 4.

The color matching functions are the tristimulus values of the equal-energy spectrum as a function of wavelength. These functions are intended to correspond to the sensitivity of the human eye. Separate sets of three color matching functions are specified for the 2 Standard Observer and 10 Supplementary Standard Observers.

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