CDLC: Choosing Lenses for Eclipse Photography

From the Canon Digital Learning Center:

Choosing a lens to photograph the upcoming total solar eclipse in August takes a lot more consideration than the camera body to be used because the camera is simply a light-tight box that records the image produced by the lens.
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Choosing a lens to photograph the sun or moon depends on how large of a sun or moon disk you want. The size of the disk is controlled by two things: your DSLR’s sensor size and the focal length of your lens.

B&H carries the gear you'll need to photograph the solar eclipse safely (checkout will be available at 9:00 PM ET tonight).