http://www.usa.canon.com/cusa/support/professional/professional_cameras/flashes/speedlite_580ex?pageKeyCode=writeReviewPage
Speedlite 580EX
10514
Features
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Approx. 25% faster recycling time compared to 550EX.
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Superior evenness of exposure, center to corner of frame.
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Slightly higher max. guide number at 105mm setting (GN 190, feet).
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Auto conversion of flash coverage with compatible digital SLRs.
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White Balance info communicated instantly to compatible digital SLRs.
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Full swivel, 180° in either direction (first TTL flash with this ability).
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AF-assist beam now compatible with all AF points on every EOS SLR.
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New Select Dial for easy inputs and user control.