What Is a Light Meter Used For?

by Contributing Writer

What Is a Light Meter Used For?
Purpose

Light meters are important instruments in the arena of photography and cinematography. They are used generally to determine the correct or appropriate photographic exposure. Most light meters come equipped with a computer which determines the best exposure for shutter speed and f-number. This is often based on the type of lighting situation and film speed a photographer or cinematographer is working with. Light meters are also used by scenic designers as well as for any typical field of lighting, such as finding ways to reduce wasteful amounts of light in homes, eliminating outdoor light pollution and creating the optimum levels of light for plant growth in nurseries. Many still and video cameras now come with built-in light meters, though most photographers continue to use handheld meters for any number of purposes.

Features

Most light meters are made out of selenium, silicon or CdS. Selenium and silicon light meters use photovoltaic sensors which produce a voltage that is commensurable to the light being exposed. Each type of sensor requires different means to produce these voltages. For instance, selenium sensors produce enough voltage to create a connection that is directed right to the meter. Silicon sensors, though, require batteries or some similar power source to operate the meter. Another type of sensor, CdS, uses photo-resistance-based sensors that also require batteries to function. Generally, light meters used today have silicon or CdS sensors. A needle galvanometer or LCD screen is used to measure the amount of light exposure in a setting.
Type

There are generally two types of light meters. One is called the reflected-light meter, while the other is the incident-light meter. Both meters serve different purposes. For instance, the reflected-light meter is used to measure the reflection of light within a scene by calibrating for proper light exposure. Meters built into cameras are generally reflected-light meters. Incident-light meters use an integrating sphere to measure how much light is falling on a particular subject. Incident-light meters also avoid the possibility of underexposure that is a common mistake when reflected-light meters are used. Unlike reflected-light meters, incident-light meters read light exposures that are separate from a subject's reflection.

Purpose