What's the Difference Between a Colorimeter, a Colorimeter and a Colorimeter?

ABSTRACT The earliest style of devices called colorimeters did not measure color. The first style of devices that actually measured color was similar to the device that did not measure color, but it was never called a colorimeter. The first style of device that measured color, and which was called a colorimeter, was an adaptation of a device that did not measure color. Much of colorimetry today is based on emulating that device. But today, the device we call a colorimeter bears little resemblance to either of the first colorimeters, other than the fact that it is designed to emulate the thing that was designed to emulate the second colorimeter. This paper provides a historical account of five different instruments that have been called colorimeters . This discussion provides insight into the technology and mindset that led to the development of the current CIE standards for colorimetry, in particular, the 1931 Standard Observer.