Canon® EOS Rebel XSi/450D Digital Field Guide

Chapter 6. The Fundamentals of Light and Exposure

In This Chapter

• The four elements of exposure

• Equivalent exposures

• Putting it all together

• Let there be light

If you're new to photography or if you're returning after some time away from shooting, the information in this chapter serves as a refresher on the elements of exposure and the characteristics of light. This chapter can also help you build a foundation from which you can expand your skills and creative options in using the Rebel XSi/450D.

The Four Elements of Exposure

Exposure is a precise combination of four elements, all of which are related to light and all of which are interrelated. If one element changes, then the other elements must change proportionally. Each element depends on the others to create a successful exposure.

Following is a summary of four elements of exposure that are discussed in detail in this chapter:

• Light. The starting point of exposure is the amount of light that's available in the scene to make a picture. The range of creative control that you have with the Rebel XSi/450D is directly related to the amount of light the camera has to work with. For every image, the Rebel XSi/450D measures, or "meters," the amount of light in the scene and bases exposure calculations on that meter reading.

  

  Figure 6.1. The Rebel XSi/450D offers excellent creative control and responsiveness. Exposure: ISO 100, f/2.8, 1/50 second, ...