When connected to the EOS-1D Mark III, the Speedlite 580EX II allows for weather resistant flash shooting and flash control via the camera’s menu system. Replacing the Speedlite 580EX, it offers faster, silent recycle times and a more durable build quality. A new Off-Camera Shoe Cord, Compact Battery Pack and Speedlite Bracket (also released today) maintain moisture and dust resistance for off camera shooting.

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http://www.the-digital-picture.com/Reviews/Canon-580EX-II-Speedlite-Flash-Press-Release.aspx