Photography A - Z the Easy Way: U - UnderexposureWriten by Eric Hartwell
Underexposure can ruin your images. But what is it?
In basic terms it is when not enough light reaches the sensor. This results in a dark, dull and lifeless image.
Why does it happen?
To capture a good image the camera chooses a combination of shutter speed and aperture according to the calculations made within the meter. Shutter speed is how long the shutter is open (and therefore, letting in light) and aperture is the size of the hole in the lens.
At most times, the camera will produce fine results and select the correct settings for the camera. Occasionally, the camera will make the wrong calculations for the subject. This is because the camera only averages the total light coming in. When shooting on manual settings, the photographer sometimes sets the wrong settings.
In these situations, there is not enough light coming into the camera. This results in underexposure. The shadows or dark areas will be too dark and featureless. Detail and information is lost.
The solution is to take the photograph again and choose MORE exposure by using a bigger aperture or a slower shutter speed. You can do this manually or you can use exposure compensation (read your camera manual to find out how).
There are situations where underexposure is common. When there is strong backlighting behind your subject, your camera will see an expanse of brightness and will reduce the exposure accordingly to produce and average result. An example of this would be someone standing in front of a large window or a subject against the sky. The backlit areas cause the camera to underexpose the subject, resulting in a virtual silhouette. In these cases try to compensate using the camera.
Eric Hartwell runs the photography resource site http://www.theshutter.co.uk and the associated discussion forums as well as the regular weblog at http://thephotographysite.blogspot.com