What does photometry mean?
Photometry is the branch of optics that deals with measuring light as it affects human vision. Its scope includes luminous flux, luminous intensity, illuminance, and brightness, and it is especially important in lighting design, astronomy, photography, and the development of optical instruments. Unlike radiometry, which measures electromagnetic radiation more generally, photometry is concerned with light as perceived by the eye. In astronomical work, photometry is used to compare the brightness of stars and other celestial objects. In engineering and architecture, it helps determine whether a lighting environment meets visual and regulatory standards. The term is technical and usually appears in scientific or technical contexts, where it conveys precision rather than casual description. Though many people encounter its results in cameras, displays, and street lighting, “photometry” itself is mainly used by specialists. Knowing the word helps distinguish the measurement of perceived light from the broader measurement of radiation.
nounPhotometry is the branch of optics concerned with measuring light, especially its intensity, brightness, and distribution as perceived by the human eye. It is widely used in astronomy, lighting design, photography, and optical instrumentation.
- The scientific measurement of the intensity, brightness, or distribution of light, particularly as perceived by the human eye.
- The branch of optics concerned with such measurements.
"Astronomical photometry revealed that the distant star was considerably dimmer than it had appeared in earlier observations."
"Astronomical photometry allows researchers to compare the brightness of stars and galaxies."
"The laboratory used photometry to evaluate the output of several types of lighting."
The plural is rare and generally occurs in technical contexts; the noun is usually treated as uncountable.
"The researchers compared stellar photometries obtained from several observatories."
Photometry is how astronomers turn a faint glimpse of starlight into a precise measure of brightness.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of photometry
Photometry was formed through New Latin from the Greek roots phōs, genitive phōtos, meaning “light,” and metron, meaning “measure.” The same Greek source underlies the combining form photo- and related English words such as photograph, photographer, photography, and photometer. The word entered English as the name of a scientific discipline concerned with the measurement of light.
Related word forms
How photometry is actually used
A formal and predominantly technical term used in scientific, engineering, astronomical, and lighting contexts. It is usually treated as an uncountable noun in general usage.
Easily confused with photometry
Photometry is the measurement of light, whereas photography is the process of capturing images on a light-sensitive medium.