Apple Aperture Digital Photography Fundamentals - Manual (Page 32)

32 Chapter 2 How Digital Images Are Displayed
Cameras with sophisticated light meters can be set to meter, or test, specific areas of
the scene. Most DSLRs allow you to choose the portion of the viewfinder to meter.
These meter settings include, but are not limited to:
 Evaluative: Evaluative metering operates by dividing the frame into several small
segments, taking a reading from each individual segment, and processing the average
of the total segments to recommend the best exposure value for the overall image.
 Spot: Spot metering operates by metering within a small target area that is usually in
the center of the frame. Spot metering is particularly useful when your subject is
placed in front of a relatively bright or dark background. Spot metering ensures that
you will correctly expose your subject. The drawback is that the background may be
incredibly under- or overexposed. This is why you should bracket (shoot multiple
exposures of the same image) when shooting in a situation that requires the use of
the spot meter. For more information on bracketing, see “
Bracketing the Exposure of
an Image ,” below.
 Center-weighted: When the camera’s light meter is set to center-weighted, the
camera measures the light in the entire viewfinder but gives extra emphasis to the
center of the frame. This setting is typically used by portrait photographers, because
the subject is usually centered and the background isn’t ignored. If the subject
moves out of the center of the frame, the meter assumes the background is the
correct exposure, leaving your subject incorrectly exposed.
It’s important to point out that light meters provide recommendations only. If the
details in the highlights of the scene are more valuable to you, you may choose to
expose the image shorter than the light meter recommends. Likewise, if the details in
the shadows of the scene are of more value, you may choose to expose the image
longer than the light meter recommends. It’s your prerogative as a photographer to
use the light meter to obtain the best exposure of the scene in your image.
Bracketing the Exposure of an Image
Even careful metering sometimes yields an under- or overexposed image. This is why
professional photographers bracket their images, whenever possible, to be absolutely
sure they have a correctly exposed image. Bracketing involves taking three shots of
the same image based on the aperture and shutter values recommended by the light
meter: one shot underexposed one stop, one shot at the recommended exposure,
and one shot overexposed one stop. Shooting the image with a range of three
exposure stops is the best way to ensure you’ll have a properly exposed image.
Note: Most DSLR models have a built-in, automatic exposure-bracketing feature.
Refer to your owner’s manual for directions about how to use it.