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 > -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
