The Canon 580EX replaced the 550EX as Canon's top-of-the-line flash. It was smaller and lighter, but more powerful, and it recycled faster than the 550EX. It was also Canon's first through-the-lens (TTL) flash to feature a full 180-degree swivel. It has an Autofocus beam assist designed to be compatible with all Canon EOS SLRs. The 580EX has since been replaced by the 580EX II.
To get started with the 580EX flash, load four AA batteries, preferably lithium batteries for longer life and faster recycling times, into the battery compartment, following the polarity diagram on the battery door. Loosen the locking ring by turning the ring counterclockwise, then slide the flash onto the hot shoe of a Canon SLR and tighten the locking ring by turning it clockwise. Turn the flash on by flipping the power switch on the back of the flash on the right side, then wait for the pilot light to go red.
The 580EX shuts off automatically after 90 seconds of idle use to conserve batteries; to turn it back on, depress the shutter button on the camera halfway or push the 580EX test-firing button.
When the pilot light turns green, the 580EX is ready for Quick Flash mode, which fires the flash at 1/6 to 1/2 power, but enables it to fire faster and works for near flash modes. For full flash, wait till the pilot light turns red. The Quick Flash only will fire in single drive mode, not in burst mode.
The 580EX has several flash modes, including Automatic or Evaluative Through the Lens (ETTL), which fires a quick preflash before firing the main flash to get the right exposure setting. The other flash modes are Flash Exposure Compensation, Flash Exposure Bracketing and Manual. The modes are all accessed by turning the mode dial on the flash. ETTL works with the Program, Aperture, Shutter and Manual modes on the camera, and is the most common mode. Flash Exposure Compensation allows you to increase or decrease the flash output up to three stops, and can be combined with Flash Exposure Bracketing, in which the camera takes three shots at different flash exposures in 1/3 stop increments.