Thinking Again About Full Auto Mode
Now that we've identified all the mechanisms that go into making an exposure, let's look again at the Full Auto mode that you've been shooting with. As you learned in Chapter 1, when you press the XS shutter button halfway down, the camera focuses and calculates an exposure. That exposure is a shutter speed setting, aperture setting, and ISO choice. The camera has determined that these settings will yield an image that is neither too bright nor too dark.
When the camera has calculated these values and autofocused, it displays its choices in both the viewfinder and rear LCD status displays. These numbers should make a little more sense to you know.
As you just learned, many combinations of shutter speed and aperture settings yield the same overall exposure. So, how does the camera choose? Its algorithms are designed to take the "safest" possible combination, that is, a shutter speed and aperture that will yield a good overall exposure, without risking handheld shake from a slow shutter speed, or image softness from an extreme aperture.
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