Use Your Built-in Light Meter

by Joyce Meck

The most technologically advanced metering option is the default Evaluate system, but don’t count on it to be the most effective for hi-key or low-key images.

Architects, engineers, lighting directors...and photographers all use light meters to measure the value of light. For years, photographers used hand held light meters to measure the levels of light in their scenes. Today, most digital cameras have highly sophisticated light-metering computers.

The light meter uses one of several built-in metering systems to measure the existing light in your scene and provides either the appropriate speed or f-stop. DSLR cameras have as many as four types of metering systems: Evaluate, Spot, Partial, and Center-weighted. Less expensive camera models may only have two or three of these options.

Evaluate is the default system because it is the most technologically advanced option, therefore is suitable for most conditions. Evaluate breaks the total area of your scene into segments and analyzes each to produce the best overall exposure, while ignoring the darkest areas.

Evaluate metering ‘evaluates’ the main subject’s position and brightness, as well as the background’s brightness and lighting. The evaluate option may also be called Multi-segment, Matrix or Pattern metering. You can be comfortable using this setting most of the time, as it will net good to outstanding results for most situations.

If it is so great, why bother to change it? Most of us have taken a backlit shot (when the background is much lighter than the point of your focus) and ended up with a silhouetted subject surrounded by a blown out white background.

For this type of shot, try using the Partial metering system, which takes into consideration only about 8% of the viewfinder’s center, preventing the object of focus from becoming just a black shape. Partial metering ignores much of the background.

      

The vulture was shot at 1/400s, f/5,6, ISO 100, 300 mm IS Lens.

Further control a difficult lighting situation by using the Spot metering mode. This setting meters a very specific part of your focused subject or scene. Metering is weighted at the center of your viewfinder and only takes approximately 3.5% of what you see into consideration to determine the correct exposure for your subject.

Center-weighted or Average metering is weighted at the exact center and is then averaged for the rest of the scene.

The two hearth examples are shot with identical settings – AV mode, Auto White Balance, f/5.0, 1/8 s, ISO 200, 75mm, no flash. The single difference was the metering system used. The Evaluate shot may be the better exposure because everything EXCEPT the darkest area was taken into consideration for the correct exposure. The ‘spot’ metering shot ignored EVERYTHING but the center area.

The two bird feeder shots also use identical settings – AV mode, Auto White Balance, 1/250 s, f/5.6, ISO 200, 380 mm, no flash. Notice the Evaluate shot has little overall contrast as opposed the Spot image.

Now, let’s go outside the box for a moment. Try these experiments:

High-Key images have little, to no, true black areas in them and may be the result of overexposure, or just the nature of the subject.

Let’s say you’d like to deliberately create a high-key image. Look for subjects that have little difference between the brightest and the darkest areas. The easiest way to create a ‘high-key’ image is to Spot Meter and base the exposure on a shadow area that still retains some detail.

Lock in the reading by pointing to the shadow area before recomposing the shot and actually firing. Take a series of exposures starting with the correct metered exposure, and then ‘bracket’ your shots by overexposing by one stop for each new exposure. Change the f-stop one stop upwards at a time and you will eventually get the result of a light, airy pastel image.

Low-Key images have minimal white, or bright, areas and might be the result of underexposure, or again, the nature of your subject. To deliberately create a low-key image, look for scenes with a broad range of shadow to bright areas, like a building or any other object with one side to the sun and the other in shadow.

Take a series of exposures, starting with the correct one using Spot Metering. Again, bracket your shots by underexposing one stop at a time. Stop down one f-stop at a time to underexpose the composition until the highlights become smaller and smaller. The result will be a moody image with sharp contrasts by forcing the mid-tones to be darker while the highlights will remain bright.

This seascape was pale and nearly blown out. By forcing the mid-tones darker and allowing the small bright areas to remain bright, I deliberately shifted the key tone for a low-key image with more drama and mood.

When exposing for Low-Key images, concentrate your exposure on the darker areas with Spot metering; when exposing for High-Key images, concentrate your exposure on the lighter areas

Get used to trying a variety of combinations to control the outcome of your shots, Combine each of the different metering modes with different ISO settings, f-stops, speeds and white balance settings to see how much control you have.

Keep shooting!