Light metering is the process of measuring the amount of available light and is used to calculate the required camera settings for the correct exposure of a photo. There are two types of light metering in photography, incident light metering and reflected light metering.
In incident light metering the measuring device is held next to the subject and measures the actual light falling on the subject. It gives a very accurate measurement but is cumbersome and time consuming to use. It is usually used in studio situations rather than field work.
In reflected light metering the light meter is located in the same location as the photographer, usually within the camera itself. This is the technique used in all automatic and semi-automatic cameras. Because it measures the amount of light reflected off the subject it is affected by the colour and reflectivity of the subject. For instance, in any given lighting situation, a black road will reflect less light than a white wall. Cameras are calibrated to expect neutral brightness subjects, so scenes with lots of light colours often end up underexposed and those with dark colours overexposed. To compensate for this, photographers sometime use a grey card or neutral brightness object in the area around them (such as grass) to set their exposure and then use those settings for the entire shoot.
In incident light metering the measuring device is held next to the subject and measures the actual light falling on the subject. It gives a very accurate measurement but is cumbersome and time consuming to use. It is usually used in studio situations rather than field work.
In reflected light metering the light meter is located in the same location as the photographer, usually within the camera itself. This is the technique used in all automatic and semi-automatic cameras. Because it measures the amount of light reflected off the subject it is affected by the colour and reflectivity of the subject. For instance, in any given lighting situation, a black road will reflect less light than a white wall. Cameras are calibrated to expect neutral brightness subjects, so scenes with lots of light colours often end up underexposed and those with dark colours overexposed. To compensate for this, photographers sometime use a grey card or neutral brightness object in the area around them (such as grass) to set their exposure and then use those settings for the entire shoot.
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