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tyPeS oF metering
All parts of a scene are often not equally important when determining the
best exposure to use. In a landscape, for instance, the exposure of the fore-
ground is usually more important than the exposure of the sky. For this
reason some cameras offer more than one metering method including the
following:- Matrix metering, sometimes called evaluative, divides the image area
into a grid and compares the pattern of measurements against a library of
typical scenes to select the best possible exposure for the current scene. This
mode is often programmed to ignore sections of the grid, such as the reflec-
tion from a mirror, that would otherwise throw off the measurement. - Center-weighted meters the entire scene but assigns the most impor-
tance to the center of the frame where the most important objects usually are
located. - Spot, or slightly larger partial metering, evaluates only a small area of the
scene. This allows you to base your exposure on a specific part of the scene
rather then relying on an average reading. This mode is ideal when photo-
graphing a subject against a bright or dark background. On some cameras
the spot that’s metered is fixed in the middle of the viewfinder or monitor. On
others you can move it, to meter other areas of the scene. - Spot AF links spot metering to the same focusing area you have selected
for focusing. Since many high-end cameras have a number of focus areas
from which you can choose, this allows you to base an exposure and focus on
an off-center subject.
Meter weighting can cause a few problems. For instance, a dark object lo-
cated off center against a very light background may not be exposed properly
because it is not located in the area the meter is emphasizing. Or, in some
cases, holding the camera vertically may give undue emphasis to one side of
the scene. These occasions are uncommon, but when they occur you can use
exposure lock or exposure compensation to get a good exposure. These tech-
niques are discussed later in this chapter.
Metering patterns
include matrix (top),
center-weighted
(middle) and spot
(bottom). The small
squares are focus areas
from which you can
choose.
By controlling metering
the exposure of this
scene was based on the
aquarium tank so the
people in the foreground
are underexposed.