How Overriding Automatic Exposure Works
When a scene is lighter or darker than middle gray you need to change the exposure to capture it the way it looks or it will be too light or dark. To lighten or darken the image many cameras let you increase or decrease exposure by two stops or more. Here are some typical settings where you'd make these changes.
- +2 is used when the light is extremely contrasty and important shadow areas are much darker than brightly lit areas.
- +1 is best for sidelit or backlit scenes, beach or snow scenes, sunsets and other scenes that include a bright light source, or very light objects, such as a white china on a white tablecloth.
- 0 (the default) is best for scenes that are evenly lit and when important shadow areas are not too much darker than brightly lit areas.
- -1 is for scenes where the background is much darker than the subject, such as a portrait in front of a very dark wall. Also good for very dark objects, such as black china on a black tablecloth.
- -2 is for scenes of unusual contrast, as when an extremely dark background occupies a very large part of the image and you want to retain detail in the brighter parts of the scene.
Top. Here are three cards that you photograph with each filling the viewfinder at the time you take the picture.
Middle. The camera's exposure system makes all three cards appear gray in the photographs. Only the middle gray card in the center is exposed correctly.
Bottom. Increasing the exposure for the white card and decreasing it for the black card captures them as they really appear. Only the middle gray card in the center doesn't need the exposure adjusted manually.