Unlike the other two units, this one offers automatic operation only, and none of the fancy features of its more expensive siblings. Its 72 guide number is a little beefier than the XSi’s built-in flash, making it a good choice as a low-power auxiliary flash unit. It lacks a zoomable flash head and offers fixed coverage equivalent to the field of view of a 28mm full-frame lens. Expect 250 to 1,700 flashes from a set of four AA batteries and recycle times of 0.1 to 4.5 seconds. The built-in AF-assist beam is linked to the center focusing point of the XSi only.