The f/number is a ratio of the focal length to the diameter of the aperture opening. The 400 at f/8, has an opening of 50mm (The actual opening may not be 50mm, depending on where in the lens the aperture is placed). It has nothing to do with the sensor or film size.
On Wed, Mar 24, 2010 at 3:18 PM, John Sessoms <[email protected]> wrote: > Also, is the actual diameter of the aperture at f/8 the same for the APS-C > sensor as it is on a film frame? [note question mark] > > The mechanical stop is going to be f/8 on the film frame. > > -- > 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. > -- Aloha Photographer Photoblog http://alohaphotog.blogspot.com/ -- 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.
