On Jun 15, 2010, at 15:49, John Francis wrote: > On Tue, Jun 15, 2010 at 03:23:26PM -0500, Bob Sullivan wrote: >> Charles, >> I get your explaination, but I look at the distances and light paths >> involved and can't imagine much of an angle at f2.8. The opening is a >> lot bigger, but that dirt has to be right on top of the sensor...and >> the light gets around it ?!! >> Regards, Bob S. > > The dust spot isn't "right on top of the sensor" - it's right on top of > the fromt surface of the protective piece of glass (and anti-aliasing > filter). If the piece of dust is smaller than 1/2.8 times the thickness > of that piece of glass there's plenty of light coming around it at f/2.8 >
Yeah, I failed to mention that. The dust is only sorta close to the sensor. If it were right on the sensor itself then the aperture would make no difference at all as the dust would block ALL light for that point. -Charles -- Charles Robinson - [email protected] Minneapolis, MN http://charles.robinsontwins.org http://www.facebook.com/charles.robinson -- 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.
