> > On Mon, Apr 06, 2009 at 10:51:37PM +0100, Bob W wrote: > > > > Ah. Thanks. Focal length is second order factor, circle > > of confusion > > > > is first order, so focal length has a greater effect on > DOF, than > > > > CoC (pixel size). > > > > > > > > > > Circle of confusion is not pixel size. > > > > I misunderstood it then. I always thought that the circle > of confusion > > represented the smallest area that could be resolved. That anything > > between a mathematical point and the CoC resolves to the same size, > > and that the physical manifestation of this on a digital > sensor was a > > pixel. > > > > This is the bit that's wrong: > > > and that the physical manifestation of this on a digital > sensor was a > > pixel. > > >
I should add that by resolved we mean resolved by the human eye, not resolved by the sensor. For example, the conventional calculation for CoC for a 4/3rds sensor, whose imaging area is 17.3mm wide, to be viewed as a 10x8" print (20x25cm) from a distance of 10" (25cm) gives a circle of confusion of 0.0173mm. If the sensor has 10,000,000 pixels on an area 17.3 x 13mm = 224.9mm, then the area of each pixel is 0.00002249mm, which is orders of magnitude smaller than the eye can resolve. Bob -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
