Yes, you are right. It's the barrel that's so much bigger. John
On Fri, 18 Aug 2006 13:31:47 +0100, DagT <[EMAIL PROTECTED]> wrote: > The size of the mirror, or in other words: the distance from the lens > mount to the film/sensor, does play a part in shorter lenses, but the > width stays the same. Remember that aperture is simply the ratio between > focal length and lens diameter. As long as you dont have retrofocus or > telecentric lenses (which are larger) the ame focal length has the same > diameter. This is more evident with longer lenses. > > And, by the way: what 50mm 2.8. Macros are different, and much larger > than the normal lenses. The front lens of an ordinary 50mm 2.8 wouldn't > be much larger than the front lens of the 40mm 2.8. > > DagT > >> Fra: "John Forbes" <[EMAIL PROTECTED]> >> >> So how do you explain the fact that a Pentax 110 1:2.8 50mm is about 1/4 >> the size of a Pentax 1:2.8 50mm in K-mount? >> >> John >> >> >> On Fri, 18 Aug 2006 10:35:13 +0100, DagT <[EMAIL PROTECTED]> wrote: >> >> > They will be smaller of you compare field of view (as a 135 2.8 is >> much >> > smaller than a 200mm 2.8), but if you compare with the same focal >> length >> > with the same maximum aperture the front element will be the same no >> > matter how small the sensor is. >> > >> > DagT >> > >> >> Fra: "John Forbes" <[EMAIL PROTECTED]> >> >> >> >> If the image circle is designed for APS-C, then the lenses will be >> >> smaller >> >> and lighter than those designed for 35mm. So they WILL be small and >> >> light, relatively speaking. >> >> >> >> But, like you, I hope they have USM. We shall know in good time. >> >> >> >> John >> >> >> >> On Fri, 18 Aug 2006 09:41:15 +0100, DagT <[EMAIL PROTECTED]> wrote: >> >> >> >> >> Fra: "John Forbes" <[EMAIL PROTECTED]> >> >> >> >> >> >> On Fri, 18 Aug 2006 10:03:00 +0100, DagT <[EMAIL PROTECTED]> wrote: >> >> >> >> >> >> > I'd give it a few months more to decide. If they are going to >> >> >> introduce >> >> >> > USM lenses it will be a logical explanation for why they have >> >> stopped >> >> >> > producing a lot of long lenses. They may be planning to revive >> >> them >> >> >> > with USM. >> >> >> >> >> >> I'm sure they will introduce more long lenses - they can't afford >> not >> >> >> to. >> >> >> At the moment, the lens line-up is unbalanced; there is lots of >> stuff >> >> >> below 50mm, and very little above 100mm. >> >> >> >> >> >> Whether the new long lenses will be USM or just small, light, DA >> >> >> versions >> >> >> remains to be seen, but if they are USM it certainly makes sense >> not >> >> to >> >> >> announce them until after there is a camera body that they can >> work >> >> >> with. >> >> >> >> >> >> I would be most surprised if there are not new 200mm, 300mm, 400mm >> >> and >> >> >> 600mm primes within two years. And, of course, the fast zooms >> have >> >> >> already been announced. >> >> > >> >> > Long lenses with larger apertures will never be small DA or D-FA >> wil >> >> be >> >> > about the same. Because of this they will also have heavy focusing >> >> > mechanisms (even if the gain some by using IF), and that is were >> they >> >> > really need USM. All of the lenses they have introduced recently >> have >> >> > light focussing mechanisms that can be drivenby the motor in the >> >> camera >> >> > without any problems. This, together with the fact that som many >> long >> >> > lenses have disappeared, make me believe that they are up to >> >> something. >> >> > >> >> > DagT >> >> > >> >> > >> >> >> >> >> >> >> >> -- >> >> Using Opera's revolutionary e-mail client: http://www.opera.com/m2/ >> >> >> >> >> >> -- >> >> PDML Pentax-Discuss Mail List >> >> [email protected] >> >> http://pdml.net/mailman/listinfo/pdml_pdml.net >> >> >> > >> > >> >> >> >> -- >> Using Opera's revolutionary e-mail client: http://www.opera.com/m2/ >> >> >> -- >> PDML Pentax-Discuss Mail List >> [email protected] >> http://pdml.net/mailman/listinfo/pdml_pdml.net >> > > -- Using Opera's revolutionary e-mail client: http://www.opera.com/m2/ -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
