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Canon EOS 40D Guide to Digital Photography by David D. Busch

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Lens Components

The typical lens, like the one shown in Figure 2.15 and 2.16, has seven or eight common features:

  • Filter thread. Lenses have a thread on the front for attaching filters and other add-ons. Some also use this thread for attaching a lens hood (you screw on the filter first, and then attach the hood to the screw thread on the front of the filter).

  • Lens hood bayonet. This is used to mount the lens hood for lenses that don’t use screw-mount hoods (the majority).

  • Zoom ring. Turn this ring to change the zoom setting.

  • Zoom scale. These markings on the lens show the current focal length selected.

  • Focus ring. This is the ring you turn when you manually focus the lens.

  • Distance scale. This is a readout that rotates in unison with the lens’ focus ...

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