On Fri 2001-11-09 (11:30), Frank Wajer wrote: > on kmp.bdimitrov.de I saw the specs of the 200 f2.5 lens. It says that the > filter > ring is 77mm, but this means that the lens cannot be f2.5, as that would > mean > a minimum 80mm filter ring! > > Can anyone explain?
A good observation. In fact it's not that easy to combine filter diameter and focal length for min. aperture, since it's not the real, outer diameter, but the inner, virtual diameter which is used. But I agree that this inner, effective diameter can't be bigger than the outer one. Such I guess that Pentax cheated - the number is incorrect. http://www.concentric.net/~smhalpin/LongComments.html#200 mm f/2.5 states that the filter diameter is 77 mm. Thus I guess that Bojidar is correct with his specs. Maybe it's just a 200/2.8, since it's smaller than the A 200/2.8 Kind regards Martin - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
