The Canon Speedlite 580EX Flash’s slightly lighter weight (compared to the 550EX) is very welcome at the end of a long hot-shoe or bracket-mounted flash shoot.
Move the Canon Speedlite 580EX Flash’s power switch to on and the flash is on – nearly instantly. The 580EX shows the ready light much faster than the 550EX. Recycle time is also reduced. Canon lists .1 to 6 seconds as the time to ready depending on flash power used. The 580EX also goes into sleep mode automatically after 90 seconds of no use (there is no SE – Save Energy power-on mode as with the 550EX). A touch of the shutter button brings the 580 back to life.