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Canon® EOS 40D Digital Field Guide by Charlotte K. Lowrie

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Chapter 8. Using Flash

In This Chapter

  • Exploring flash technology

  • Using onboard flash

  • Modifying flash exposure

  • Using flash control options

  • Using one or more accessory Speedlites

Countless scenes, whether lit from the top, side, back, or barely lit at all, open the door for using flash–either the EOS 40D's onboard flash unit or one or more accessory Canon EX-series Speedlites. And on the creative front, flash offers opportunities for capturing everything from a drip of water to stroboscopic motion.

This chapter explores flash technology, details the use of the 40D's onboard flash, and the menu options for the built-in flash and for accessory EX-series Speedlites. This chapter is not an exhaustive look at all the ways in which you can use the onboard or accessory flash units. Rather, the focus of this chapter is on fundamental flash techniques and ideas for using flash for both practical situations and creative effect.

Exploring Flash Technology

Both the onboard flash and Canon's EX-series Speedlites employ E-TTL II technology. E-TTL stands for Evaluative Through-the-Lens flash exposure control. E-TTL II is a flash technology that receives information from the camera including the focal length of the lens, distance from the subject, exposure settings including aperture, and the camera's built-in evaluative metering system to balance subject exposure with the ambient light.

In more technical terms, with E-TTL II, the camera's meter reads through the lens, but not off the focal plane. After the ...

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