Quantifying colour

Complex visual effects, such as pearlescence, translucence, iridescence and glitter, help sell many products, including cars, cosmetics, pharmaceuticals and military hardware. A new instrument at the US National Institute of Standards and Technology (NIST) makes comprehensive measurements of such appearance properties to help companies calibrate their own tools and control product quality.

Exotic surfaces and coatings may look different depending on illumination or viewing angles, subtleties that cannot be accounted for by traditional characterisation methods. Many consumers are familiar with automobile paints that appear to change colour with viewing direction.

The new NIST device, called a goniospectrometer, automatically measures the colour of light reflected from a surface as well as its dependence on the directions of illumination and observation.

NIST already offers a heavily used calibration service making less sophisticated measurements with another instrument. The new goniospectrometer will provide more complete data on the reflection of light from a colour surface, and will be used for calibrating similar instruments and for research on exotic-appearing materials and coatings.