Photography

Exposure Compensation and White Balance

Exposure Compensation

Most of the time the camera's light metering works fine on choosing the proper exposure settings. However there are certain scenes when the camera's metering algorithms can be fooled or does not match your preferred output. You can tell the camera to brighten or darken the output of its metering using Exposure Compensation. Typical Exposure Compensation ranges are "+/- 2 EV at 1/3 EV interval". That means that you can increase the exposure up to 4 times (+2 stops) or reduce it down to 1/4 (-2 stops) its normal level. "1/3 EV interval" indicates that each step you increase or decrease in the Exposure Compensation value you are increasing or decreasing the amount of light by 1/3 stop.

Depending on the manufacturer, Exposure Compensation is implemented in the camera either by varying the aperture while maintaining the shutter speed or varying the shutter speed while maintaining the aperture. Sometimes both values are varied together. In order to have a general idea of how much increase or decrease in exposure your particular camera will provide when you adjust the Exposure Compensation value, it is recommended to get 3 reference shots: 1 using normal metering results, 2 using a positive Exposure Compensation (+1 EV) and 3 using a negative Exposure Compensation (-1 EV). This process is called Exposure Bracketing. Some cameras can do this automatically using Automatic Exposure Bracketing (AEB). With this feature, the camera will take one shot using normal metering exposure, another using a positive Exposure compensation (usually +1/3 EV but can be changed by user) and a third shot using a negative Exposure compensation (usually -1/3 EV but can be changed by user).

White Balance

This is the camera's way of correcting colors by using white as a reference. The camera tries to ensure that a white object in real life will also appear white in the pictures. Wrong coloration is often introduced by environment or artificial lighting often identified according to temperature. The following is a table of Color Temperatures of common Light Sources.

Most cameras offer some preset WB values to adjust the overall color of a photograph based on different possible light sources that often causes bluish, reddish, or green hues on the pictures.

Automatic White Balance (AWB) - This setting analyzes the screen and decides a White Balance adjustment between 3000K to 7000K.

Custom WB or User - The user can tell the camera to use a reference white by taking a picture of a gray area under the current lighting. The camera then uses this as a White Balance reference for succeeding photos.

Tungsten or Incandecent - Corrects the yellowish hue caused by Incandecent bulbs or similar light sources.

Fluorescent - This is used when taking pictures under fluorescent lighting. Some cameras have two settings for Fluorescent since the intensity of light coming from fluorescent lamps from different manufacturers vary depending on their production standards. Some flurescent lamps are even calibrated to produce daylight white.

Daylight - Useful for taking pictures under normal daylight.

Flash - This corrects the slightly yellowish hue of a typical Xenon Flash lighting. In some cameras this is omitted since Flash is similar to Daylight hue.

Cloudy - Even under ordinary daylight, when it is cloudy the color will tend to have a bluish hue. Use this setting to correct the color.

There are other more specific WB settings, mostly self-explanatory. Other cameras also provide an option to adjust the White Balance based on specific color temperatures.