A photometer measures the intensity of light.
A photometer is a device used to measure light intensity . The term is formed by the compositional elements photo- (which refers to light ) and meter (referring to measurement or a device used to measure ).
Before continuing, it is important to note that, in the field of physics , light is the name given to the electromagnetic wave that is recorded in the visible spectrum (that is, in the area of electromagnetic radiation that can be perceived by the human eye). The idea of intensity , meanwhile, refers to a level of force.
How a photometer works
The photometer is a device that measures the quantity of photons present in a beam of light. At this point it should be clarified that photons are the elementary particles that, according to the criteria of quantum physics, make up electromagnetic radiation .
What the photometer does is analyze the light that its photosensitive cell receives. These instruments were invented at the end of the 19th century in England , replacing the measurement of light that was carried out through the use of chemicals.
Depending on their characteristics, photometers can measure incident light (measuring the level of light reaching an object) or reflected light (i.e. the light reflected by objects back onto themselves). Both are important in the field of photography .
Photometers are very important in photography.
Its use in photography
To measure the light in an environment or on a stage, a photometer is essential. Thanks to the photometer, you can calculate the correct exposure and thus take the best photos.
Nowadays, cameras have an internal photometer that performs this task . However, when at a professional level you want to work with the greatest possible accuracy, photographers often resort to an external photometer or handheld photometer .
In many cases, a very precise photometer is needed to obtain the best image recording. When lighting is poor, there are marked contrasts, there are several lights shining simultaneously or a white background is detected, photometers are necessary to measure the light accurately and allow for the appropriate adjustment.
The photometer in astronomy
Astronomy is the science that studies the laws, movements and characteristics of celestial bodies. Celestial bodies that can be seen at night for their brightness are called stars .
Since photometers are used to evaluate the intensity of radiation emitted by an object, in astronomy these devices make it possible to measure the brightness of stars . Specifically, they usually transform the light they receive into an electrical signal.
Photometers are usually installed in the focal plane of a telescope . This way, they can measure the light coming from stars. Today, however, CMOS or CCD sensors are often used to perform the same function.