Search results
Results From The WOW.Com Content Network
The use of the human eye as a detector led to photometric units, weighted by the eye's response characteristic. Study of the chemical effects of ultraviolet radiation led to characterization by the total dose or actinometric units expressed in photons per second. [1] Many different units of measure are used for photometric measurements.
This forms the important relationships found between sets of stars in colour–magnitude diagrams, which for stars is the observed version of the Hertzsprung-Russell diagram. Typically photometric measurements of multiple objects obtained through two filters will show, for example in an open cluster, [24] the comparative stellar evolution ...
The advanced photometers then could be used either to measure the light from the potential picture as a whole, to measure from elements of the picture to ascertain that the most important parts of the picture are optimally exposed, or to measure the incident light to the scene with an integrating adapter.
In astronomy, a photometric system is a set of well-defined passbands (or optical filters), with a known sensitivity to incident radiation. The sensitivity usually depends on the optical system, detectors and filters used.
In photometry, luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye. The SI unit of luminous intensity is the candela (cd), an SI base unit.
Photometria is a book on the measurement of light by Johann Heinrich Lambert published in 1760. [1] It established a complete system of photometric quantities and principles; using them to measure the optical properties of materials, quantify aspects of vision, and calculate illumination. Title page of Lambert's Photometria
The UBV photometric system (from Ultraviolet, Blue, Visual), also called the Johnson system (or Johnson-Morgan system), is a photometric system usually employed for classifying stars according to their colors. It was the first standardized photometric system.
Quantity Unit Dimension [nb 1]Notes Name Symbol [nb 2] Name Symbol Luminous energy: Q v [nb 3]: lumen second: lm⋅s : T⋅J: The lumen second is sometimes called the talbot.: Luminous flux, luminous power