Understanding Your Camera's Metering, Exposure Compensation and White Balance Settings

Recently, I wrote a post on understanding light, which touched upon different types of light and the color of light. While I briefly referenced white balance and metering in my previous post, I thought it would be best to explore these settings in greater depth because you must understand metering, exposure compensation and white balance in order to properly account for light. Therefore, below you will find an explanation of the metering, exposure compensation and white balance settings on your camera and how to use each setting.

Metering

Metering is how your camera determines what the correct shutter speed and/or aperture should be depending upon the amount of light that enters the camera. Every camera usually has three different metering options, generally referred to as "center-weighted," "spot/partial," or "matrix (Nikon)/evaluative (Canon)." Each option works by assigning a relative weighting to the light in your scene.

Metering Modes: Center-Weighted, Matrix and Spot 

With center-weighted metering, the camera assigns greater weight to the amount of light in the center of the image. As such, the camera calculates exposure primarily based upon the amount of light that is or is not present in the center of the frame.

Matrix or evaluative metering is the default setting on most DSLR cameras. It works by dividing the frame into numerous subsections (or zones) and then analyzes a variety of factors, including the location, intensity and/or color of the light in each subsection, in order to determine proper exposure. The metering system will usually assign greater weight to the area around the focus point.

Spot or partial metering offers the photographer the greatest control over exposure. Spot metering works by evaluating only the light around your focus point to determine exposure. By focusing on only the area around your focus point, you can ensure your intended subject is properly exposed even if the rest of your image is under- or over-exposed. Some Canon models offer partial metering, which is similar to spot metering except that the covered area is larger.

Knowing the Correct Metering Zone to Use

For most situations, matrix or evaluative metering will suit your needs. I tend to use matrix or evaluative meeting when shooting landscapes or headshots. Center-weighted is a good choice when you want to prioritize the middle of the frame. For example, it might be useful in a close-up portrait. Since spot metering offers the greatest control over exposure, you want to use this setting in situations where your intended subject occupies a smaller area of the frame and it is essential that your subject is properly exposed. For example, when taking photos of the moon, you will want to use spot metering to ensure the moon is properly exposed. Additionally, you should use spot metering when creating silhouettes.

Exposure Compensation

Exposure compensation enables you to adjust the exposure measured by the camera. The camera will evaluate the appropriate exposure based upon the metering mode you select, but the final exposure target will be altered based upon the exposure compensation value you have selected. You can adjust the exposure by either instructing the camera to allow more light in or less light in.

How and When to Compensate for Exposure

The exposure compensation button on your camera is marked with a "+/-" icon. The plus (+) setting makes your image brighter, while the minus (-) makes the image darker. Adjustments are made in the form of stops. Stops represent an increase or decrease in the amount of light that the camera will allow as compared to what the metering mode would have otherwise done. Most cameras allow for up to 2 stops of exposure compensation at 1/3 stop intervals. Therefore, an exposure compensation value of +2 or -2 represents either a doubling or halving of light compared to what the metering mode would have done otherwise. A setting of zero is the default and it means no exposure compensation is being applied.

Exposure compensation is essential in situations where you are shooting in either low-light or high-contrast scenes. However, the amount of exposure compensation needed will vary depending on your subject and the metering mode that you are using. When making use of exposure compensation, you will just have to experiment to find the right value.

Exposure Bracketing

Generally, when taking an important photo I use exposure bracketing. Exposure bracketing involves taking one image using the camera's measured exposure, a second image using positive exposure compensation and a third image using negative exposure compensation.

Many digital cameras now contain a setting called "Automatic Exposure Bracketing." Using this setting, the camera will automatically take a properly exposed, an underexposed and an overexposed image each time you press the shutter release button. Some cameras allow you to specify your exposure compensation value, as well as, the number of over- or under-exposed images that you desire.

For example, my camera allows me to set the automatic bracketing feature to take up to 5 images at 1/3 stop intervals. Therefore, using this setting, I would have two underexposed images, two overexposed images and one properly exposed image and the exposure compensation values for the two under- or over-exposed images would differ by 1/3 stop.

I realize this may sound a bit confusing so I encourage you to start experimenting with this setting on your camera in order to better understand this feature.

White Balance

White balance determines how accurately the colors in your photo appear and involves removing unrealistic color casts so that objects that appear white in person also appear white in your photo. In order to best understand white balance, you need to understand color temperature.

Understanding Color Temperature

As explained in my previous post on understanding light,color temperature is the temperature at which a blackbody would emit radiation of the same color as a given object. A blackbody is an object that absorbs all incident light--neither reflecting it nor allowing it to pass through. Color temperature relates to the color of light produced from a particular light source. Color temperature is measured in degrees Kelvin (or K). Warm colors are those at lower temperatures and cool colors are those at higher temperatures.



Color Temperature Chart

White Balance Settings

 

Camera white balance takes into account the color temperature of a light source. While the camera's auto white balance will suffice for many situations, there will eventually come a point where you need to adjust your camera's white balance settings so it is important to know and understand the different white balance settings on your camera.
 
Auto: As cameras become more sophisticated, the auto white balance tends to perform better in most situations. However, you might be able to get better results using a different mode.
 
Daylight: This mode is pretty self-explanatory; it is used for shooting outdoors under normal daylight settings.
 
Shade: Shaded locations generally produce cooler or bluer pictures. Therefore, you will need to warm up your subject by adjusting with this preset.

Cloudy: Again, this mode is pretty self-explanatory. You will want to use this setting when shooting outside on a cloudy day because it will warm up your subject.
 
Tungsten: This setting compensates for the warm light that comes from the incandescent bulbs in your home. It is usually used when shooting indoors to cool down the warmer color temperature in your photos.
 
Fluorescent: This setting compensates for the very cool, bluish light produced by the fluorescent lighting you tend to find in offices and hospitals. Again, it is usually used when shooting indoors and it will warm up the color temperature in your photo.
 
Flash: Another self-explanatory setting; this mode compensates for the colorcast caused by the camera's flash.
 
Custom: This setting can be used to set white balance manually using a gray card.
 
Temperature: This is another setting that allows you to adjust white balance manually. This is a setting utilized most often by professional or serious photographers, however, feel free to experiment to your hearts content.