Colorimeters (7.24)
Colorimeters -- manufactured by several companies -- were designed to replace or perhaps enhance color-grading master stones by using a fiber-optic light system to digitally measure the color of a diamond. The accuracy is claimed to be within a half a grade of the actual “true” color. Prices are still relatively high considering that technology costs drop with time and innovation.
A colorimeter works by transmitting a focused beam of light through the material being measured, recording the absorption or transmission of that light's behavior. This data is then used to determine the concentration of a substance of the material, based on the Beer-Lambert Law, or to compare the color to a known standard.
Due to the higher price tags of these specialized instruments many would prefer the old school master stone comparisons. Although for the higher volume dealers this would likely be a very good investment.
Review and compare all the specs to be sure you choose the colorimeter that fits all your needs the best.
Above image courtesy of: https://www.ogisystems.com/diacolor.html
Above image courtesy of: https://imageminc.com/?page_id=585
Above image courtesy of: https://www.mehta.tools/products/eos-colorimeter-for-polished-diamonds