Exposure meter

The use of light meters in photography for optimally exposed photos

Exposure matched to the subject plays a fundamental role in photography. To achieve this, the light meter is of central importance, which is the subject of this article. In the course of this, you will also receive information about the use of the meter as well as the zone system of Ansel Adams.

What are light meters?

The light meter can be used to measure the brightness of the object to be photographed in order to make the appropriate settings for the aperture and exposure time on the camera. Almost all modern cameras have an integrated light meter that converts the measured values into an exposure value (automatic exposure) or allows manual settings. There is also the option of external metering. These handheld exposure meters are mostly used by professional photographers who work with artificial light (flash, continuous light) in the photo studio.

What are light meters used for?

Exposure meters can measure the amount of light falling on or reflected from a subject. Especially when the light intensity is not uniform within the photographed scene, setting the appropriate values using the light meter can make the difference between a properly exposed photo and a poor one. Cameras with built-in light meters use reflected light metering, where the reflected light from the camera is used to measure exposure. External exposure meters, on the other hand, measure the amount of light falling on a subject, for which the meter is placed near the subject. In contrast to reflection metering, the light is measured before it can be reflected by the subject. This incident light measurement also allows the light output of several flash heads used to be measured individually, which means that the various light sources can be controlled separately.

How to use a light meter?

When using the built-in reflected light metering, readings should be taken from different areas of the subject, for example dark shadow areas, bright light areas, and center zones. The meter can then automatically average the final exposure value and apply it to the camera's settings. For incident light metering, the external meter should be held in front of the camera. When doing this, make sure that the same light in the scene also falls on the exposure meter. After pressing the exposure meter button, the results can be read and the shutter and aperture of the camera can be adjusted accordingly

Zone system by Ansel Adams

The Zone System is a standardized way of working that guarantees correct exposure in any situation. The scale consists of eleven tonal values, the darkest value is pure black, the lightest value is pure white. Consequently, black is zone 0 and white is zone 10. The zones are defined by Roman numerals, with the middle tone value being in zone V (5) and having a reflectance of 18%. For digital photographers, zones 3 to 7 are particularly relevant, so that the darkest part of a subject is in zone 3 and the lightest part in zone 7. Consequently, everything below zone 3 is underexposed and everything above zone 7 is overexposed. For example, if the metering was based on a dark object in the background (Zone 3), photographers will need to underexpose by two stops from the average Zone 5 to reasonably expose the photo. Gray cards that are in the gray midtone (Zone V) serve as an additional tool for metering exposure.