The F-number is defined as the ratio between focal lengh and aperture diameter,AFAIK.
In my A720IS, I can have F/4.8 at max zoom,i.e. 35mm focal length. So shouldn't I get larger than F/2.8
aperture in full wide angle,i.e. 6mm focal length? ( 35/4.8 is much more than 6/2.8 ) Please correct me if
I'm wrong.I'm willing to accept larger aperture even at the cost of shallow DOF & more purple fringing!