What is "photometry"

Photometry \Pho*tom"e*try\, n. [Cf. F. photom['e]trie.] That branch of science which treats of the measurement of the intensity of light.

n. 1 (context physics English) the measurement of various aspects of light, especially its intensity 2 (context astronomy English) the measurement of the intensity and spectrum of light from stars

n. measurement of the proterties of light (especially luminous intensity)

Photometry is a technique of astronomy concerned with measuring the flux, or intensity of an astronomical object's electromagnetic radiation. When photometry is performed over broad wavelength bands of radiation, where not only the amount of radiation but also its spectral distribution is measured, the term spectrophotometry is used.

The word is composed of the Greek affixes photo- ("light") and -metry ("measure").

Photometry can refer to:

• Photometry (optics), the science of measurement of visible light in terms of its perceived brightness to human vision
• Photometry (astronomy), the measurement of the flux or intensity of an astronomical object's electromagnetic radiation
• Spectrophotometry, the measurement of spectral distribution along with the flux or intensity
• A photometric study, sometimes also referred to as a lighting "layout" or "point by point"
• Photometric stereo, a computer vision technique also known as "shape from shading"

Photometry is the science of the measurement of light, in terms of its perceived brightness to the human eye. It is distinct from radiometry, which is the science of measurement of radiant energy (including light) in terms of absolute power. In modern photometry, the radiant power at each wavelength is weighted by a luminosity function that models human brightness sensitivity. Typically, this weighting function is the photopic sensitivity function, although the scotopic function or other functions may also be applied in the same way.