Summing Up
I've thrown a lot of theory at you in this chapter, and it's worth spending a little time studying it. However, the rest of this book will reinforce these theories with actual practice.
To sum up, it takes a certain amount of light to yield an image that is neither too bright nor too dark. Your camera offers two ways to control this light: shutter speed and aperture. Shutter speed allows you to control how still or blurry a subject is, while aperture lets you control how deep the depth of field in your image is. In addition, ISO lets you control how light sensitive the sensor is.
All these controls are measured in stops, with a change of one stop representing a doubling or halving of light. These three parameters have a reciprocal relationship, which means that if you change one, you can alter one of the others to make up for that change and ensure that your overall exposure remains the same.
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