A powerful flash with a maximum guide number of 58/191 at ISO 100 in meters/feet (at 105mm focal length), This Speedlite replaces the 550EX and features faster recycling, more consistent color and enhanced controls The Speedlite 580EX flash is compatible with Canon's E-TTL II (Evaluative Through The Lens) auto exposure technology. When combined with a compatible Canon camera, E-TTL II utilizes subject distance and other information that automatically modifies flash power, resulting in accurate flash exposure regardless of subject size, reflectance, or photographic composition. The Speedlite 580EX flash is compatible with all film and digital EOS cameras as well as G-series and Pro-1 PowerShot digital cameras. The flash includes two features especially for digital photography. EOS 20D and EOS-1D Mark II** digital SLR users will especially appreciate the Speedlite 580EX flash's ability to auto-compensate for the size of the CMOS sensor, and zoom the flash head automatically to match the effective focal length conversion. This feature allows the Speedlite 580EX flash to maximize the efficiency of its light distribution and produce more flashes from a set of batteries. When used with the EOS 20D or 1D Mark II** digital SLR cameras, the flash and camera communicate to make fine adjustments to auto white balance by electronically monitoring the charge level of the batteries and the duration of each flash burst, resulting in consistently accurate color for every sh