Camera Basics #08 - What is exposure metering?

Exposure metering systems - what are they?

The camera needs a white balance to cope with different types of light. Your camera has a number of predefined white balance settings, for example:

The camera's light meter is used to measure the brightness of the subject. The data obtained from this is used to determine the exposure, and the aperture value and exposure time are adjusted in automatic mode. Basically, automatic exposure metering is used in full automatic, program automatic and semi-automatic camera modes and forms the basis for the automatic calculation of the camera settings. For photographers who select all camera settings such as time, aperture and ISO themselves, exposure metering can help them to find the right parameters.

In the past, external exposure meters were used for this task. However, the disadvantage of this method was that it was very time-consuming. On the other hand, it encouraged the photographer's creativity, as they had to judge for themselves which areas in the image should be exposed and which should not.

TTL (Through the Lens) metering replaced the external exposure metering systems. In the various photo modes (e.g. landscape or portrait), the camera can now select the exposure itself and adjusts it according to the subject.

Spot metering

The spot metering only takes into account a very small part of the image to determine the brightness, which contains between two and five percent of the image area. More precisely, this image area is located around the AF spot. This allows the photographer to select the image area that they want to expose correctly with extreme precision. The disadvantage of this is that small changes to the image section can lead to striking changes, especially with very heterogeneous subjects. (For example: dark subject in direct sunlight) Spot metering ensures that the captured detail - in the middle of the image - is reproduced with the brightness of the middle gray explained at the beginning. If the captured detail does not correspond to this, all other tonal values in the image are shifted towards light or dark accordingly. This measurement is therefore very susceptible to errors and leads to strong changes in the exposure . The actual strength of spot metering lies less in the individual measurement and more in the ability to analyze the contrast and brightness range of a subject.

Center-weighted integral metering

A modification of multi-segment metering is center-weighted integral metering. In this case, multi-segment metering is supplemented by the activated center autofocus field. The focus is on the center of the viewfinder; the most important part of the image should be in the center. Based on the fact that the main subject is usually in the center of the image, this image area is weighted higher in the metering. A bright or dark environment has just as little influence on the measurement result as unimportant small details. The good old center-weighted integral metering delivers a hit rate in the range of 80-90%, but is easier to correct than multi-segment metering.

The special clue: automatic exposure bracketing

With this function, your camera takes three pictures at different exposures. In addition to the normal exposure, there is then a series of images that are more and less exposed by the preselected EV value. This allows you to see immediately which exposure is optimal for your picture!

A little task for you:

• Photograph a subject several times using different exposure metering methods and observe the differences in exposure. There is no such thing as perfect here, it is more important that the exposure corresponds to your expectations and that no areas of the image are left without detail.