In article <4ohk1l$sag@useneta1.news.prodigy.com>, KLGQ84A@prodigy.com says...

>I recently purchased a Sigma 24-70 Aspherical lens. Could someone
>explain what aspherical means and/or does? I know it's suppose to make
>sharper images at the edges and at extreme f stops. Thanks for the help.

An "A-Spherical" (or non-spherical) element does no magic, as I understand
it, but just allows the designer to eliminate an element that otherwise
would be required in the design for a similar level of performance.
Hope This Helps