Troland

Part of speech: noun

Definitions

1. A unit of measurement for the amount of light focused on the retina of the eye, calculated as the product of luminance and pupil area
2. A photometric unit expressing the intensity of light stimulating the retina, determined by multiplying the scene's luminance by the effective pupil diameter
3. A standard unit quantifying retinal illumination, derived from the luminance of the visual field and the area of the eye's pupil opening

Etymology: The troland is a unit of retinal illuminance, the amount of light reaching the eye, and it is named after Leonard Thompson Troland, an American psychologist and physicist who worked on vision at Harvard. He proposed the unit to give vision researchers a single measure that combined the brightness of a light source with the size of the pupil through which it entered the eye. Rather than describing light only as it leaves a lamp or screen, the unit describes how much of it actually reaches the retina. The word is a straightforward eponym: a surname turned into a unit name, following the pattern of other units honoring scientists, such as the watt and the kelvin. Its formation is simple, and its importance lies in its purpose. It allowed researchers comparing experiments to speak in the same terms about how bright a stimulus appeared to the eye.