Indeed it does, and it is a meaningful, though ignored, consideration (or should be) to users of longer zooms, especially. Typically, the zooms' worst optical performance is at the "long" end. And the worst performance at the long end is almost always at the smaller apertures. (Occurs both because of base performance plus diffraction effects at the high numerical aperture). The small end stop becomes smaller by the same factor as the large-end stop (as do all the numerical apertures; the lens mfr expects the camera's meter to compensate. So, assume a 100 to 300mm f/3.5 to 5.6 zoom which has a diaphragm numerically scaled from f/3.5 to f/22 -- very typical. These lenses tend to test out at f/4 to f/6.3 in the real world. At the 300 end, instead of f/22, the aperture will be closer to about f/37 to f/45. (You can calculate for yourself the diffraction effects...) Of course, Joe VacationPhotographer will be blithely using the lens stopped down to try to increase "depth of field"... Not nice! Don Feinberg donf@cybernex.net Vocatus atque non vocatus, deus aderit... > I have a follow-up question though. What about the minimum aperture on > these lenses ... does it too drop in corresponding fashion? It would > seem so but not necessarily, no? I don't have one of these variable > aperture zooms. > > andy > >
