Every time you half-press the shutter button, your camera measures the light in the scene and decides how bright the photo should be. This is called metering. Most of the time it works so well that you never think about it. But when it goes wrong, you get gray snow, dark faces against bright skies, or washed-out stage photos. In this lesson you will learn how the meter thinks, why it makes mistakes, and how to choose a metering mode that measures the part of the scene you care about.
What is metering?
Metering is the way a camera measures the brightness of a scene to decide the exposure. The camera has a built-in light meter that reads the light bouncing off the scene through the lens. In automatic and semi-automatic modes, the camera uses this reading to set the exposure. In Manual mode, it shows the reading on a scale so you can decide.
The meter's big rule: middle gray
The light meter has a simple goal: make whatever it measures look medium bright, halfway between black and white. Photographers call this middle gray, often described as 18% gray.
The meter cannot tell what color or brightness things really are. It does not know that snow is white and a black cat is black. It only measures how much light comes back, and then aims for middle gray.
| What the meter measures | What it does | Result |
|---|---|---|
| A normal mixed scene | Averages to medium | Usually looks right |
| Mostly white (snow, white wall) | Makes it darker to reach gray | Too dark: white looks gray |
| Mostly black (dark stage, black cat) | Makes it brighter to reach gray | Too bright: black looks gray |
This is why exposure compensation exists, as you learned in exposure compensation. And it is why choosing what the meter measures, using metering modes, can solve many problems before they happen.
The main metering modes
Metering modes decide which part of the frame the meter pays attention to. Brands use different names for similar modes.
| Mode | Also called | What it measures | Best for |
|---|---|---|---|
| Matrix / Evaluative | Matrix (Nikon), Evaluative (Canon), Multi (Sony) | The whole frame, divided into zones and analyzed intelligently | Most everyday scenes; the default |
| Center-weighted | Center-weighted average | The whole frame, but with extra importance on the center | A subject in the middle with a bright or dark background |
| Spot | Spot (some cameras also have Partial, a slightly larger spot) | Only a small area, often a few percent of the frame, at the center or the focus point | Exact control: a face on a dark stage, a backlit subject |
| Highlight-weighted | Highlight-weighted (on some cameras) | Tries to keep the brightest areas from turning pure white | Stage lights, bright dresses, scenes with strong highlights |
Matrix or evaluative metering
This mode divides the frame into many zones and compares them, often using the focus point, colors and distance. Many modern cameras also recognize faces. It is smart and works well for most photos, which is why it is the default. It still follows the middle-gray rule, so very white or very dark scenes can fool it.
Center-weighted metering
This mode reads the whole frame but gives most of its attention to the middle. It is simple and predictable: if your subject is in the center, the meter mostly measures your subject. It is useful when the background is much brighter or darker than your subject.
Spot metering
Spot metering measures only a small spot and ignores the rest of the frame. This gives you exact control, but you must point the spot at the right thing. Remember the middle-gray rule: if you spot meter a white shirt, the camera will make it gray and the photo too dark. Spot meter something of medium brightness, such as a face, green grass or blue sky away from the sun, or use exposure compensation.
Remember:On some cameras the spot is always in the center; on others it follows your focus point. Check your camera's manual so you know where your spot is.
Measure, lock, then reframe
Sometimes the part you want to measure is not where you want it in the final photo. The solution is to lock the exposure. Most cameras have an AE-L button (auto exposure lock), often marked with a star or AE-L.
- Point the camera at the part you want to measure, for example a person's face.
- Press AE-L to lock the exposure. On many cameras, a half-press of the shutter also locks it.
- Move the camera to the composition you want, while keeping the lock.
- Take the photo. It uses the exposure you locked, not the new view.
Which metering mode should you use?
| Situation | Good choice |
|---|---|
| Most everyday photos, even light | Matrix / Evaluative |
| Centered portrait with a bright background | Center-weighted, or spot on the face |
| Performer under a spotlight on a dark stage | Spot on the face, or highlight-weighted |
| Person backlit by a sunset | Spot on the face, then lock (or use compensation) |
| Very bright scene such as snow | Matrix with plus compensation |
With Manual mode, you can measure a scene once and keep the settings. The meter scale then simply shows you how your choice compares with what the meter would choose. You will learn how to check the final result more precisely in histogram and exposure evaluation.
Common mistakes
- Spot metering a very bright or very dark area: the meter turns it gray and the whole photo is wrong.
- Forgetting spot metering is on: everyday photos then change brightness wildly as the spot moves. Switch back to matrix afterwards.
- Trusting the meter in tricky light: snow, stages and backlight usually need your help.
- Locking exposure, then the light changes: a lock only fits the light you measured.
How professionals meter
Most professionals leave their camera in matrix or evaluative metering for most of their work, because modern meters are very good, and they use exposure compensation for the tricky scenes. They switch to spot metering when the important subject is small and surrounded by very different brightness, such as a speaker on a stage. Above all, they understand the middle-gray rule, so they can predict the meter's mistakes before they happen.
Practical examples
A friend in front of a sunset
- Situation
- Your friend stands in front of a bright sunset, and every photo shows their face almost black.
- What to do
- You switch to spot metering, measure your friend's face, lock the exposure, and reframe.
- Why it works
- Matrix metering was trying to keep the bright sky medium, which darkened the face.
- Result
- Your friend's face is well exposed; the sky is brighter, but the person is clear.
A speaker on a conference stage
- Situation
- A speaker stands in a spotlight with a dark screen and empty stage behind them, and photos look washed out.
- What to do
- You use spot metering on the speaker's face.
- Why it works
- The large dark areas made the camera brighten the whole photo; spot metering ignores them.
- Result
- The speaker's face is correctly exposed and the background stays dark.
Key points
- Metering is how the camera measures light to decide exposure.
- The meter aims to make whatever it measures look middle gray, so white and black scenes fool it.
- Matrix/evaluative reads the whole frame; center-weighted favors the middle; spot reads a small area.
- Use AE-L to measure one part of the scene, lock it, and reframe.
- Matrix plus exposure compensation handles most scenes; spot helps with small subjects in extreme light.
Frequently asked questions
What is metering in photography?
What is the best metering mode for beginners?
When should I use spot metering?
What is middle gray?
Conclusion
Your camera's meter is a helpful assistant that always aims for middle gray. Understand that rule, choose a metering mode that measures what matters, and use exposure lock or compensation when the scene fools it. Next, you will learn to read the histogram, the most reliable way to check exposure.
Finished reading? Track your progress through Exposure and metering.