On Wed, Apr 6, 2011 at 10:06 AM, steve harley <[email protected]> wrote:
> interesting technique, and thanks for sharing, but it doesn't seem intuitive > that spherical aberration alone can describe soft focus > > a thought experiment: if you aimed a soft-focus lens at just the right > concave surface, would everything be sharp? i think there'd still be more > going on You're confusing spherical aberration with field curvature. Spherical aberration is an on-axis aberration; it's what you get from a spherical telescope mirror instead of a parabolic mirror. If you have rays of light from a point source on axis (i.e. at field center), rays of light at the edge of the mirror/lens come to a different focus than rays that pass near the center. So even a single star at the center of the field is blurred. It was the aberration that afflicted the Hubble Space Telescope at launch. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
