On 9 Mar 2005 at 14:13, Juan Buhler wrote: > On Wed, 9 Mar 2005 15:14:32 EST, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > > > Obviously a small (higher) f stop shows up fine detail that might get > > blurred > > with a shallower depth of field. > > > This is precisely what is not obvious to me. If the dust is on the > front element of the lens yes, it will be more visible at smaller > apertures. But we are talking about sensor dust, which is right on the > sensor, without a lens to "focus" it.
Think of it this way and remember that the surface with the dust is suspended over the active area of the sensor: At wide apertures the image forming rays pass through the lens over the entire aperture opening and all focus at the film/sensor plane so the image forming rays are coming from a wide range of angles so any object suspended above obscures only a relatively small area of the image forming rays.. At narrow apertures the image forming rays pass though a narrow opening hence that are conformed to pass though the dusty filter above the sensor surface at limited angles hence anything in their path will be rendered as a more obvious shadow on the image forming plane. Cheers, Rob Studdert HURSTVILLE AUSTRALIA Tel +61-2-9554-4110 UTC(GMT) +10 Hours [EMAIL PROTECTED] http://members.ozemail.com.au/~distudio/publications/ Pentax user since 1986, PDMLer since 1998
