How to measure color using spectrometers and calibrated photographs

The measurement of color in biology has become increasingly common. These measurements are not limited to color vision research, but are also found in studies of communication, signaling, camouflage, evolution and behavior, and in the examination of environmental, artificial and biogenic light. Although the recent availability of portable spectrometers has made it simpler to measure color, guidance on how to make these measurements has not kept pace. Because most biologists receive little training in optics, many measure the wrong thing, or measure the right thing in the wrong way. This Commentary attempts to give biologists a brief overview of how to measure light and color using spectrometers and calibrated photographs. It focuses in particular on the inherent ambiguities of many optical measurements, and how these can be addressed.