Excerpt: The new Canon Speedlite 580EX is that latest in Canon's evolution of high end, shoe mount, speedites. From the 430EZ to the 540EZ, 550EX and now the 580EX, power output and features have increased. The new 580EX is, of course, E-TTL (and E-TTL II) compatible, and it has a guide number of 58/191 (meters/feet) at ISO 100 and 105mm focal length. It's both smaller and lighter than the 550EX which it replaces.
Excerpt: Accessory flashes such as Canon Speedlite 580EX II Flash are some of the most important pieces of equipment in my kit. The 580EX II is Canon's top-of-the-line, professional grade external flash - There are very few features missing in this one.