Metering mode is the method by which your camera evaluates the exposure of a scene using the built in light meter and shows in the metering level scale of the camera.
A metering level scale in the camera will look similar as shown the below:
Graphical representation of exposure scale
Types of Metering mode
There are 3 main types of metering modes:
- Matrix or Evaluative
- Center metering
- Spot metering
There are also some additional metering modes which are specific to camera brands and will be a hybrid of these three modes.
Working of Light Meter in Camera
The camera has an inbuilt reflective light meter which measures the reflecting light in a scene and tells you the exposure.
The light meter works on the principle of 18% grey or middle grey. It works as follows :
- Shadows are converted to shades of black and dark grey.
- Highlights and bright colors are converted to shades of light grey and white.
- And midtones are converted to mid-grey.
- The light meter perceives darker shades of grey as underexposed, mid-grey as correctly exposed, and lighter shades of grey as overexposed.
Your light meter then averages out all the grey shades to determine the overall exposure of your scene. This is displayed in the Exposure scale of the camera.
Understanding Exposure scale of the camera
Camera exposure scale can be found in the settings menu or in the viewfinder of your camera.
In the camera exposure scale :
- The values range from negative three to positive three.
- Negative values indicate an underexposed scene.
- Positive values indicate an overexposed scene.
- And an exposure value of zero indicates a properly exposed scene.
When you adjust your exposure settings (Aperture/Shutter Speed/ISO), your exposure value will change accordingly. Ideally when setting your exposure the goal is to have an exposure value of zero or close to zero.
Understanding metering modes
The metering modes in camera , analyses the exposure of a scene using a particular logic and displays it in the metering scale. Let us look at the three main types of metering mode
1.Matrix/Evaluative Metering
Matrix metering goes by several different names depending on the camera brand. It is referred to as evaluative metering,verage, multi-segment, and even zone metering in some of the camera brands.
Regardless of the camera brand, this metering mode applies the same logic when determining your scene’s exposure.
In Matrix metering mode the entire scene is divided into sections and the average of exposure of the sections is taken as the final exposure of the scene.
The algorithm of calculation can differ in each camera brand, but the output of matrix metering mode will be the average exposure of the entire scene.
Matrix metering will produce an image with the most average exposure.
Below is a graphical representation of Matrix metering mode :
When is Matrix metering mode used
- Matrix metering mode is good to start shooting when you are learning photography basics.
- It suits a situation where the scene is evenly lit up.
- Landscapes and wide angle photography, the scene is so large that there can be numerous variations in light. In such situations matrix metering gives good results.
- Matrix metering does not work well in contrast light situations.
2.Center-weighted Metering
In this metering mode the light in the entire scene is taken into consideration, but the exposure in the center of the frame is given additional priority in determining the exposure. Below is the graphical representation of center-weighted metering:
The size of the center portion of the image may differ depending on the camera brand you are using. Some DSLRs allow you to adjust the size that your camera treats as the center.
When is Center weighted metering used
- Center-weighted metering is most effective when your subject is at the center of your frame.
- Portrait and abstract photography will benefit the most from shooting in center-weighted metering.
- This mode works well when your subject is in the center of the frame and filling 60-70 % of your frame.
- In backlit situations this mode can be used to determine creative exposures.
3.Spot Metering Mode
This mode evaluates one specific section of your image and determines the exposure using that “spot” while ignoring the rest of the image. The spot is the determined by the position of your focus point.
Spot metering considers a small portion around the focal point in your scene. The area covered can vary in different camera models, but will be not more than 5% of the scene.
Only considering a small portion of your image can have benefits, but there are also disadvantages.Spot metering ensures a specific portion of your image is properly exposed. But, this can result in the rest of your photo being overexposed or underexposed.
Spot meter depends on the position of your focal point, and depending on how dark or bright is the spot, you can drastically change the contrast of your image.
For example, if you choose a dark area of your image, it will make your entire image brighter. Likewise, if you select a bright area of your image, it will make your entire image darker.
Remember Spot metering never averages the exposure , and hence you need to be in good understanding of the light in the scene while using it.
When is Spot metering used
- Spot metering is most effective if your subject only takes a small portion of your image.
- Spot metering is also great for creating silhouettes.
- While shooting high-contrast scenes, spot meter can give creative exposure results.