This Dorr Power Zoom Flash for Canon cameras offers a powerful zoom in a relatively compact body. This Dorr flash unit has a guide number of 42 and an 85mm focal setting with an ISO 100 Flash Range up to 15 metres. The aperture setting on this flash is f2.8, although this does depend on the lens' TTL flash control. The number of flashes of this flash is approx 150-1500 flashes per set of batteries. There is also an extendable reflector plate to partially direct lighting with a bounce flash. This Power Zoom Flash also has an automatic shutdown, flash-ready indicator, exposure indicator and takes 4 AA batteries and weight 278g (without batteries inserted).