subject: A Beginner's Guide to Metering and Exposure [print this page] A Beginner's Guide to Metering and Exposure
In photography, exposure is the amount of light allowed to enter the camera, thereby making the image brighter or darker depending on the exposure time. If the shutter is open too long, the picture becomes overexposed, and far too bright. On the other hand, if the shutter is too quick, not enough light enters the camera, leaving the image dark and unusable. Clearly, the amount of exposure is an important part of photography.
Fortunately, modern digital cameras make this much easier. By using a light meter, digital cameras can automatically fine-tune an image's exposure, resulting in better pictures.
However, while the camera can determine the relative brightness or darkness in a photograph, sometimes it does not produce the image you had in mind. Fortunately, many cameras provide several metering options to help take that perfect picture.
The majority of photographs use average metering. This method simply uses the whole image to determine the exposure time, resulting in consistent brightness values throughout the image. Most of today's camera's use a more advanced method that breaks up the image into several sections, determines the best exposure for each, and then recombines them, resulting in a more detailed image. Depending on the camera, this may also be known as evaluative, matrix, multi-zone, or honeycomb metering.
For pictures with a greater focus on a single subject, centre-weighted metering may be a better option. In this mode, the camera is most sensitive to the centre of the image, and so giving it the most "weight," or importance. This method still leaves the surroundings visible, which can give a nice balance to the picture. It can also be used to capture a silhouetted subject, by working harder to properly expose appropriate area. This is the second most commonly used metering method.
In some cases, such as wildlife photography or extremely backlit subjects, spot metering is very useful. In this mode, the camera will only expose a very small section of the photograph, usually 5% or less of the image, ignoring the rest. For instance, spot lighting is excellent for photographing the moon, as it will ignore the darkness of the surrounding space, showing much more detail. Most cameras will automatically focus on the centre of the viewfinder; however some may allow you to adjust the focal point.
Finally, some cameras may offer a partial metering option, which is essentially spot metering over a larger area, around 10% to 15% of the image. Use partial metering when the edges of the image would badly affect the lighting of your subject.
Using this information, you should now know which option will work best for you.
