Should you bother to learn about metering modes? I’m confident I can sell you on it. Your camera’s automatic metering will only carry you so far. As your digital photography ability grows, you’ll start to feel frustrated in scenes with mixed light. Learning metering modes is the key to making tricky light conditions seem much less intimidating.
What is metering?
This is vital to understand before you learn about your camera’s individual metering modes. “Metering” means taking a light reading. A properly exposed image is made up of three tones of light: the shadows, mid-tones, and highlights.
The image below demonstrates these three tones well. The forested hills in the foreground and dark cloud represent the shadows, the temple roof and figure represent the mid-tones, and the bright clouds represent the highlights.
Taking light readings from the scene
Your camera’s metering modes control which part (s) of the scene your light meter uses to take a reading. Consider the example below. If you were to meter only off the dragon and take the photo, the dragon would be correctly exposed. However, the sky would probably be too bright.
Alternatively, if I was to meter only off the sky, the sky would be correctly exposed but the dragon would be a bit too dark. However, if I metered from a wider section of the scene, I would get a more balanced exposure.
The four main metering modes
Now, let’s get down to the crux of the article. Here, I’m going to explain what each of your camera’s four metering modes does and how this affects your images.
But before we begin, a note about how your camera meter works. Very bright and dark tones can trick your light meter. Why? Because it is designed to bring every tone to something called “18% gray.” Imagine a snow-covered mountain or a jet black car. Would you want your camera to correct these tones to appear 18% gray? Or would you want their tones to be rendered as truly as your eye sees them? The answer is obvious, but not to your light meter.
So it is your job to review your image on the histogram and decide if it is correct for your scene or not. If it’s not you can use Exposure Compensation to adjust it (when shooting in Aperture or Shutter Priority modes).
Evaluative (or Matrix) Metering Mode
Evaluative metering is the natural mode to explain first because it’s the one your camera uses as standard or default. Your light meter takes a reading from across the whole scene. With that information, your camera’s onboard computer makes multiple calculations to determine a correct exposure with balanced highlights, mid-tones, and shadows.
Center-Weighted Metering Mode
Imagine that you’re now zooming into the frame slightly. Whereas Evaluative Metering mode reads the light from across the entire scene, Center-Weighted Metering mode reads light with a preference towards the middle. It still reads from a large proportion of the frame, just not the whole thing. This varies between camera manufacturers, but it’s usually between 60 % and 80 % of the frame.
Partial Metering Mode
If Center-Weighted metering meant zooming in a little, Partial Metering is a huge jump inwards again. This time, your light meter will read the light from an area the size of 6-15 %2pan>