| Re: what does a fast lens actually mean
a 'fast' lens refers to the fact that a large aperture allows a faster shutter speed to be used. This is obviously desirable when using long lenses. As you point out, though, a large aperture will give you limited DOF so is not always desirable. However, in poor light a large aperture may be the only way to get a shutter speed fast enough to avoid camera shake (or blurring of a moving subject matter).
Matt |