Flash & Lens Coverage
The Canon 580 and 430 series flashes have a zoom head. Both flashes have the coverage of lenses from 24mm to 105mm. The flash talks to the camera and ask for the lens setting and will adjust accordingly, through the fancy of the electronics … Canon calls it the E-TTL II.
What about for a Canon 7D, the T3i, the 1DMk4, the… the crop/APS-C or APS-H sensor cameras? The flash knows the camera and the flash understands the lens/sensor settings. The flash will adjust the flash coverage automatically, only if you are in the E-TTL mode. This does not apply to the flash manual mode.
The Manual vs E-TTL mode is on the flash and has nothing to do with the camera settings. The camera can be in P, Av, Tv or M and the flash still be in E-TTL.