LESSON 59
Metering modes
How the camera decides what is right.
IN THIS LESSON
- What the meter assumes
- The modes
- Correcting the meter
- In practice: a simple routine
What the meter assumes
The metering mode is the way a camera measures light to set exposure. Most cameras offer spot, centre-weighted and multi-zone modes, and some add partial and average. Every reflected-light meter has the same blind spot: it tries to make what it measures a middle tone. A white snowfield or a black cat therefore come out wrong unless you correct. The source notes that an average reading of a snowy landscape can be underexposed by two stops or more, because the meter darkens what it thinks is too bright. Knowing what each mode measures tells you when to trust it.
The modes
Spot metering reads a very small area, about 1 to 5 percent of the frame, usually the centre or the focus point. It is not swayed by anything else, which makes it good for a backlit face, the Moon, or an actor on a dark stage, and it is the method the zone system relies on. Partial metering reads a larger circle, about 10 to 15 percent. Centre-weighted metering concentrates on the central 60 to 80 percent and fades toward the edges. Average metering treats the whole frame equally. Multi-zone metering, also called matrix or evaluative, measures many points, from several to over a thousand, and combines them in a way each maker keeps to itself.
Correcting the meter
Exposure compensation adjusts what the meter suggests. Most cameras allow up to two or three stops either way, in steps of a third or a half, and some allow more. One stop doubles or halves the light. In aperture priority, compensation changes the shutter time; in shutter priority it changes the aperture. So for snow, add one to two stops; for a dark subject filling the frame, take some away. In complex light, the source notes that professionals often switch to manual exposure rather than rely on the camera.
In practice: a simple routine
This section is working practice. Leave the camera on multi-zone for everyday work, because it handles most scenes. Switch to spot when a small subject matters and its surroundings are much brighter or darker, then meter the subject itself. In manual mode, meter something that really is a middle tone, such as grass, a grey road or a weathered stone, and keep that setting while the light stays the same. On a digital camera, check the histogram after the first frame; lesson 10 explains how to read it. The meter is a guide. The picture you want decides the exposure.
| Mode | Area measured | Good for |
|---|---|---|
| Spot | about 1 to 5 percent | backlit faces, the Moon, stage light |
| Partial | about 10 to 15 percent | bright or dark edges you want to ignore |
| Centre-weighted | central 60 to 80 percent, fading out | a central subject |
| Average | the whole frame equally | even scenes |
| Multi-zone | many zones compared | everyday shooting |
Try it today
- 01Photograph a white wall in multi-zone metering with no compensation.
- 02Repeat with plus one and plus two stops, and note which looks white.
- 03Do the same with a dark surface and minus compensation.
- 04Ask a friend to stand against a bright window and compare multi-zone with spot on the face.
- 05Meter green grass in manual, keep the setting, and shoot three different scenes in the same light.