On Sun, 20 Sep 1998 02:04:33 +0100, "Paddy Lavin" wrote:

>Apart from depth of field and controlling the amount of light
>that gets to the film, does changing the aperture value do
>anything else?

YES!!! Depending on lens type and quality, it can make a
just noticeable, or an extreme, difference in lens sharpness...
The best lenses are almost always improved some in optical
perfomance by stopping down at least a bit - the worst are
usually vastly improved by using small stops (around f16).
The best, though, will show image quality reduction due to
diffraction when stopped down below about f8 (though it will
not be serious enough to worry about until around f22...).