Metering modes

Learning goal

You will be able to choose which part of the frame the camera measures light from. You will explain that matrix metering divides the whole frame into zones and weighs them, that center-weighted metering gives priority to the middle, and that spot and partial metering look at a small area; you will tell in which scene each one is useful and in which it goes wrong; you will use spot metering together with what you learned about middle gray in the previous lesson; and especially in backlight or in front of a bright background, you will expose faces correctly by correcting the reading for the skin's tone.

The question

When you photograph someone sitting in front of a window, sometimes the face stays in the dark and sometimes the window blows out pure white; yet it is always the same light, the same window, the same person. Most of the time the difference lies in where in the frame the camera is looking. If the camera looks at the whole frame and takes the bright window into account, it darkens the face; if it looks only at the face, it burns out the window.

Where in the scene is the camera looking? Many cameras can give a few different answers to this question, and you choose the answer. These options are called metering modes. In this lesson we will talk about which part of the frame each metering mode looks at, in which scene it is useful, and which one to turn to, and when, to expose a face correctly.

Context

The lesson of Lesson 9.1, in short, was this: whatever the camera looks at, it tries to pull toward middle gray. When you metered the baker's apron, the black mouth of the oven and a gray card, you got three different results. The metering mode decides how large this "area it measures" is and where in the frame it sits. The same scene is exposed differently in different metering modes.

Metering modes are usually shown with small icons in the camera's menu or quick settings: a rectangle standing for the whole frame, a circle with an emphasized middle, or a small dot in the middle. Their names change with the manufacturer; one may say "matrix", another "evaluative" or "multi-zone", which is why the first mode is often written as matrix / evaluative metering. On phones, metering is usually hidden and adjusts to the point you tap on the screen. Whatever the names, there are four basic approaches: looking at the whole frame, giving priority to the middle, looking at a medium-sized area, and looking at a very small point.

Simple explanation

How does matrix metering look?

Matrix metering divides the whole frame into many zones and measures the brightness of each zone separately. Then it combines these readings with a calculation: some cameras give more weight to the zone where the focus point is, some bring a face forward when they detect one in the scene, and some notice a bright sky or a dark corner and try to reduce its effect. The details of this calculation change from manufacturer to manufacturer and are usually not disclosed.

Matrix metering is a good start in most scenes and is the default mode of many cameras. In a landscape with balanced light, on a street, in an everyday family photo, it usually makes a correct suggestion. Where it struggles is in scenes where a large part of the frame is very different in brightness from the subject: a face in front of a bright window, a musician under a single spotlight on a dark stage, a small figure under a wide sky. In these scenes, matrix takes into account not the subject but the brightness or darkness that dominates the scene as a whole.

What is center-weighted metering for?

Center-weighted metering also looks at the whole frame, but gives the middle of the frame much more weight than the edges. The middle area decides most of the reading; the edges still contribute a little. This mode is the approach that was common in old film cameras, and it is still found on many cameras today.

The biggest advantage of center-weighted metering is that it is predictable. Unlike matrix's complex calculation, what it does is clear: it looks at the subject in the middle of the frame. It is useful in portraits where you place the subject in the middle, or in scenes where an object in the middle matters. But because it still looks a little at the edges, a bright pane of glass or a dark curtain behind still affects the reading; just less than with matrix. If the subject isn't in the middle, for example if it is placed toward the edge with the rule of thirds, center-weighted metering may measure not the subject but the empty area in the middle.

When are spot and partial metering used?

Spot metering measures a very small part of the frame, most often a small circle in the middle or the area around the focus point you chose, and ignores everything else. Partial metering works in a similar way, but looks at a somewhat larger area than spot metering. These two modes are the most powerful tools when there is a big difference between the scene as a whole and the subject's brightness: an actor under a spotlight on a dark stage, a face standing in backlight, a bird in front of a bright sky.

The strength of spot metering is also its responsibility. The middle gray assumption from Lesson 9.1 comes fully into play here: spot metering measures a small area and pulls that area toward middle gray. If the point you measure is mid-toned, the result is right; if it is a white shirt, the photo darkens, and if it is a black coat, it brightens. That is why with spot metering you either measure a mid-toned point, or you know the tone of the point you measure and add compensation. Spot metering is the most precise tool for someone who knows what they are measuring; for someone who doesn't, it is the mode that goes wrong most easily.

How does the metering mode affect faces?

In portraits, the choice of metering mode directly decides the tone of the face. When you photograph a face with a bright pane of glass or an open sky behind it using matrix metering, the camera takes the bright background into account and darkens the face; this is more noticeable on skin darker than a mid tone, because the difference between face and background is bigger. Cameras that offer face-detection metering ease this problem, but don't always solve it completely.

Measuring the face directly with spot or partial metering takes the background out of the calculation. But because spot metering will pull the face toward middle gray too, a correction is needed for the skin's tone: if the spot was placed on a dark cheek, the result comes out lighter than it really is and needs a little minus; if it was placed on a light cheek, the result slides toward gray and needs a little plus. Which point of the face you put the spot on also matters: a shiny point on the forehead and a cheek in shadow give different results. A part like the cheek, which takes the light evenly, is often a good start.

Visual evidence

Imagine photographing a grandfather reading a newspaper in a dark room, by the light coming from the bright window behind him. The grandfather's skin is dark, and behind the window is a sunny garden. First you shoot with matrix metering. The window and the garden are in the right tones, but the grandfather's face is almost a black silhouette; you can't even make out the pages of the newspaper.

You switch to center-weighted metering; the grandfather is in the middle of the frame. His face has opened up a little but is still dark, because the reading still takes in the window's brightness from the edges. Then you switch to spot metering and put the spot on the grandfather's cheek in shadow. The face brightens, but a little too much: his dark skin has slid into a pale, ashy gray. You give two-thirds of a stop of minus compensation. Now the grandfather's face is back to its natural depth; his eyes behind his glasses and the lines of the newspaper can be made out. The window is pure white, but that is a conscious choice: the photo tells the story of the grandfather, not the garden.

Common mistakes

Summary

Metering modes decide where in the frame the camera looks: matrix divides the whole frame into zones and weighs them and is a good start in most scenes, center-weighted gives priority to the middle and is predictable, and spot and partial metering look at a small area and offer the most precise tool when the difference between subject and background is big. Because spot metering pulls the point it measures toward middle gray, you need to know that point's tone; in portraits, measuring the face removes the background's effect, but you need to correct for the skin's tone, a little minus on dark skin and a little plus on light skin, and zoom in on the face to check.

Mini assignment

In this assignment you will shoot the same difficult scene with four metering modes.

1. Seat a friend in front of a bright window and shoot the same frame with matrix, center-weighted, partial and spot metering, without adding compensation.
2. Compare how the face and the window are exposed in the four frames, and note what each mode looks at.
3. With spot metering, measure your friend's cheek in shadow and expose the face correctly by adding compensation for the skin's tone.
4. Put the same spot reading once on a white shirt and once on a dark fabric, and see how the result goes off.

Check yourself

• Can you explain why the four metering modes give different results in the same scene?
• With spot metering, how did the tone of the point you measured affect the result?
• After compensation, does your friend's face look its own skin tone and stand apart from the background?

Glossary

Mini quiz

1. Why can a face in front of a bright window come out dark with matrix metering?

• A) Because matrix metering measures only the face
• B) Because matrix metering looks at the whole frame and takes the bright window into account
• C) Because matrix metering only works at night
• D) Because the window isn't in the frame

2. What is the biggest advantage of center-weighted metering?

• A) That what it does is clear and predictable
• B) That it doesn't measure the edges at all
• C) That it measures only one point
• D) That it always exposes faces correctly

3. When you measure a white shirt with spot metering, how does the photo come out?

• A) It is exposed correctly
• B) It comes out too bright
• C) Its colors change
• D) The white shirt turns a dirty gray and the photo darkens

4. If, after measuring a cheek darker than a mid tone with spot metering, the skin looks pale, what do you do?

• A) Give plus compensation
• B) Go back to matrix metering
• C) Give a little minus compensation to bring back the skin's depth
• D) Raise the ISO

Answers

1. B — Matrix metering weighs the whole frame; the bright window's large area affects the reading and the camera darkens the face.
2. A — Center-weighted metering makes it obvious that it is looking at the middle; predicting the result is easier than with matrix's complex calculation.
3. D — The small metering area sees only the shirt; this light surface is taken for strong light and the frame darkens.
4. C — Because the dark cheek is darker than an average tone, the camera opens up the frame too much; a few clicks toward minus give back the face's natural depth.

Summary card

• Matrix: the whole frame, divided into zones; a good start.
• Center-weighted: the whole frame, but the middle counts most; predictable.
• Spot and partial: a small area; the most precise tool in difficult light.
• Spot pulls the point it measures toward middle gray: know the point's tone.
• If you spot-metered the face, a little minus on dark skin, a little plus on light skin; zoom in and check.

Bridge to the next lesson

Whichever metering mode you choose, the fastest tool for correcting the camera's suggestion has always been the same small button: the one marked with plus and minus. We have used this button in many lessons but never looked at it on its own. The next lesson shows in detail why that small button matters so much and how it corrects the camera's decision with a single touch.