The Textbook of Digital Photography - PhotoCourse

ChApter 3. Controlling exposure

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how oVerriding AutoexPoSure workS

When a scene is lighter or darker than middle gray you need to adjust the

exposure to capture the scene the way it looks in real life. To do so many

cameras let you increase or decrease exposure in autoexposure modes 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 night scene or 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 in night scenes where 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.

1. Here are three cards
   that you photograph
   with each filling the
   viewfinder at the time
   you take the picture.


2. 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.


3. 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.

+2 (^0) -2
Underexposing by
2 stops kept the
background dark while
correctly exposing the
spotlit areas.