Un photometer It is a fundamental tool in the world of photography and astronomy that helps us measure the intensity of light. It's like a little electronic brain that sits in our cameras or that we carry separately in the form of a portable device. The term is formed with the compositional elements photo- (light) and -meter (device used to measure). Photometer applications are quite important in this world.
Therefore, we are going to dedicate this article to tell you everything you need to know about a light meter, its characteristics and importance.
What is a photometer
A photometer is an instrument used to measure the intensity of light. Its main function is to determine the amount of light available in a scene or the appropriate exposure level to take a properly exposed photo.
The photometer consists of a device that has a photosensitive cell, generally a photodiode, which is capable of detecting incident light. This cell converts the light into an electrical signal, which is then processed and displayed on the photometer's measurement scale.
The use of the light meter is essential for photographers and cinematographers, since it allows them to get accurate and consistent results in terms of exposure. By measuring the intensity of light in a scene, the light meter helps you determine the right combination of aperture, shutter speed, and ISO to achieve the correct exposure. To better understand light in photography, you can research ashy light.
There are different types of photometers, such as handheld ones, those integrated in the cameras or the independent ones. Handheld light meters are portable devices used by holding them close to the scene to be photographed. On the other hand, some camera models include built-in light meters that measure light through the lens and provide a readout directly in the viewfinder or on the camera screen. For more detailed information on devices that assist in image capture, it may be helpful to review the Venus temperature mystery.
Applications in astronomy
Photometers also have important applications in the field of astronomy. In astronomy, the study of celestial objects and astronomical phenomena requires precise measurements of light from space.
Astronomical photometers are instruments specially designed to measure the amount of light emitted by stars, galaxies, nebulae, and other celestial objects. These light meters typically have high sensitivity to pick up even the weakest light signals. These devices are used in various research areas. For example, they are used to measure the brightness of stars and galaxies, which allows to determine its intrinsic luminosity, its distance and other important parameters to understand the structure and evolution of the universe.
They are essential in the study of transient phenomena such as supernovae, gamma-ray bursts, and novae. By measuring changes in brightness from these events, these devices allow astronomers to detect and study these phenomena, which in turn provides valuable information about the astrophysical processes involved.
They are also used for the search and characterization of exoplanets. By measuring subtle variations in a star's brightness caused by an exoplanet transiting in front of it, photometers can help identify and study these distant planets. This is an important aspect in the observation of light in different contexts and is also related to space phenomena, as mentioned in the article on Asteroid Juno.
Types of photometers
There are basically three types of photometers: those that measure reflected light, those that measure incident light, and those that can measure both types of light. To better understand how they work, you can review the concepts of speed of light.
Reflected Light Photometer
A reflected light photometer measures the light reflected from the person or object we are photographing. This means that the exposure value given by the reflected light meter will depend on the object's hue, since a lighter-skinned object or person reflects more light than a darker-skinned object or person. In other words, people with light skin will have different exposure values than people with darker skin. To better understand how different types of light work, you can consult .
incident light photometer
This type measures the intensity of actual light from the scene that falls on the subject regardless of the object or person we are photographing and gives us the corresponding exposure value. That is to say, it does not matter if the object is white, black or brown, the exposure value that it provides us is the same.
Operation
We have already commented that a photometer measures light (reflected or incident) and gives us exposure values that in principle are correct for the light of the scene in front of us.
With the reflected light meter integrated in our camera, it is important to correctly select the type of measurement required for each scene and understand how to interpret the results, since the correct or incorrect exposure of the shot will depend on it. These are the types of measurement that exist:
- Matrix: It takes exposure references from different points distributed in the frame and proposes an average exposure according to the different lights. It is suitable for most situations where the contrast between light and shadow is not obvious.
- Punctual: measures exactly the point that we indicate in the scene, focusing on it and ignoring the rest of the lights. It works well when there is a big difference in light between our center of interest and the rest of the scene.
- Partial: similar to spot, but covers more of the image to assess exposure.
- center weighted: Performs measurements in the central area of the image that it prioritizes, although it takes into account the rest of the lights in the scene.
Again, we have to choose the shooting mode. If we choose manual mode, we will have to adjust the values of the exposure triangle based on what the camera's built-in exposure meter tells us.
If we choose the priority mode, the photometer will give us the value of another variable of the exposure triangle. On the other hand, if we choose the automatic mode, the camera will make any necessary shutter speed, aperture, and ISO adjustments as it sees fit.
Once the measurement mode and the shooting mode have been selected, we have to interpret the measurements provided by the photometer and we do so through the histogram. The histogram helps us to know if the exposure is correct. That is, not only if we make the correct adjustment so that the measurement in the photometer is at "0", but also if we can correctly interpret the exposure that it gives us, finally obtaining an image according to the scene.
I hope that with this information you can learn more about the photometer, its features and applications.