The Canon EOS Digital Rebel XSi/450D Companion

CHAPTER 7

THE LIGHT METER REVISITED

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e Light Meter Revisited

In Chapter 1, we looked at the XSi’s light meter, which analyzes the light in your

scene to determine an exposure that will yield an image that’s neither too light

nor too dark.

e light meter is activated every time you half-press the shutter button, and

while the automatic metering in the XSi is very good, it can be confused and

won’t always calculate the best exposure for every scene. For example, consider

this image:

is image suffers from bad backlighting, which is leaving

the subject’s face in shadow.

We’ve looked at a bad backlighting problem before. Because of the bright back-

ground, the camera is biasing its metering toward the brighter portion of the

image, and the resulting exposure leaves the person underexposed. But you’ll find

that other problems can also crop up from mismetering, most notably, an inabil-

ity to render black tones as real black. We’ll look at both of these problems and

see how they can be easily addressed using a few simple tricks and controls. Let’s

start with the backlighting problem.

Metering Modes

By default, the XSi uses an evaluative meter system for its light metering. e XSi’s

evaluative meter divides your scene into a grid of 35 zones. e brightness of each

zone is measured, as well as the contrast between zones, the size of your subject,

the brightness of your ...