All dSLR cameras contain built-in light meters which accurately calculate exposure settings based on each individual scene. In shutter priority, aperture priority, or manual mode, the light meter must be correctly balanced to insure accurate exposures.
Thankfully, using these meters is simple if the photographer understands their individual uses and limitations.
Measuring the Entire Scene with Evaluative Metering
Most cameras’ default setting is an evaluative meter. Represented by the [.] symbol, this metering mode evaluates the entire scene within the viewfinder when calculating the overall average exposure.
Today’s cameras are so accurate, that this system works well in most situations, however it excels when diffused or consistent lighting is found throughout the entire scene.
If a scene is overly bright, like a white-sand beach, the meter will often underexpose the image. To properly expose a photograph in this situation, a photographer will often need to override the settings by using exposure compensation (represented by +/- symbols) to +1 or +1.5. In dark scenes, the opposite is true. The photographer will need to manually adjust the exposure compensation to -1 or -1.5 to avoid overexposure.
Taking Portraits with Center-weighted Metering
Represented by the (.) symbol, the center-weighted meter is nearly identical to evaluative metering, except it focuses only on the center portion of an image, while ignoring the edges of the frame.
This mode is ideally suited for portraits and group shots, because the background is of less importance than the subject.
Dealing with High Contrast Scenes Using Spot Metering
While the center-weighted or evaluative meter balance the entire scene, the spot meter, represented by a simple . symbol, measures only a small portion of the image. This metering mode is ideal in high contrast scenes when a well-defined subject must be accurately exposed.
To use the spot meter, adjust the location of the focusing marker until it is completely filled in by the subject. The camera will calculate the exposure to accurately portray the subject, while ignoring the rest of the scene.
Five Things to Remember About Built-in Metering
- Take advantage of the Camera’s LCD screen by taking a test shot when the situation permits. Adjust the exposure as required
- After using the spot or center-weighted metering system, return the camera to the default evaluative meter to avoid incorrect exposures later in the day.
- All meters read and react differently to different scenes. Practice and experience will often prove irreplaceable when confronted with a scene requiring quick decisions.
- Avoid including too much bright sky in the initial frame. Evaluative meters will underexpose the entire frame and lose detail in the darker foreground. Simply recompose the image to include the sky after selecting the proper camera settings.
- Move closer to the subject to meter important elements of the scene in high contrast situations. After selecting the camera settings, move back to recompose the desired photograph and take the shot.