That's one piece of anectdotal evidence. But unless you can show that the optical design of the two lenses is the same it doesn't really offer much to support your position. After all, Pentax managed to come up with (proportionally) larger differences in size and weight between "K" and "M" lenses.
In any case, nobody is saying all DA & DFA lenses *must* be the same size. It's just that for telephoto lenses there's a certain minimum size a lens must be (because the size of the front element is determined by the focal length and the max aperture, and the length is determined by the optical design). The existing FA lenses are already pretty close to that minimum, so there's no way to make a DA lens much smaller. The K-mount lens you quote is just about at the minimum diameter needed for a 600mm/f5.6 - it takes 112mm filters. (The 133mm diameter must be measuring the outside of the lens hood, not part of the optical body of the lens). a little larger than the minimum needed for a 600mm/f5.6 (my FA 250-600/f5.6 takes 112mm filters) close to the minimum On Sun, Sep 03, 2006 at 11:02:23AM +0200, Jostein ?ksne wrote: > Adam, Paul, > > There is evidence that flies right in the face of your statements. > Take 600mm f/5.6, for example (links below). This is a convenient > comparison because it exists in both 645 and K mount A-series. The > only dimension being smaller for the 645 is length. I haven't done the > maths, but it would not surprise me if that difference comes from the > different register distances. > > Weight leaps up a whopping 68% from K to 645. The front element > diameter is also larger. > > > The K-mount: > Lenght: 386 mm > diameter: 133 mm > Weight: 3280 g > > The 645: > Length: 353 mm > Diameter: 156 mm > Weight: 4800 g > > > Whatever logic there is to DA lenses having to be the same size as DFA > certainly isn't supported by this line of argument. > > Thinking about it, the DA/DFA may be a different ballgame since they > apply to the same bayonet and register distance, but I don't see why > it should be. I'd love to be enlightened though. > > Links: > Boz' K-mount page: > http://www.bdimitrov.de/kmp/lenses/primes/extreme-tele/A600f5.6.html > > or http://tinyurl.com/h9gju > > and B&H: > http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=40765&is=USA&addedTroughType=categoryNavigation > > or http://tinyurl.com/kckmh > > Jostein > > > On 9/2/06, Adam Maas <[EMAIL PROTECTED]> wrote: > > Shorter optics are bulkier in MF, longer optics are not, and the > > deciding point is usually around 200-300mm. The size exception is where > > they neck down to meet the mount (as 35mm mounts are notably smaller). > > In fact the 35mm version should be slightly longer in most cases (to > > cover the difference in Register). > > > > -Adam > > > > > > Jostein ?ksne wrote: > > > Point about front element taken, but the front element is not THE > > > single factor in deciding the weight of a lens. > > > I have five lenses for the 645 system, and all of them are heavier, > > > and bulkier, than their K counterparts. > > > > > > Jostein > > > > > > On 9/2/06, Digital Image Studio <[EMAIL PROTECTED]> wrote: > > > > > >>On 03/09/06, Jostein ?ksne <[EMAIL PROTECTED]> wrote: > > >> > > >>>Then tell me, guys, > > >>>Why are the medium format optics so much larger for corresponding > > >>>focal lengths and max apertures? > > >> > > >>The long lenses aren't, I had a 400/4 for my 67, it didn't taper much > > >>as the back end used the external bayonet but the front end was no > > >>bigger than a 400/4 in any format. > > >> > > >>-- > > >>Rob Studdert > > >>HURSTVILLE AUSTRALIA > > >>Tel +61-2-9554-4110 > > >>UTC(GMT) +10 Hours > > >>[EMAIL PROTECTED] > > >>http://home.swiftdsl.com.au/~distudio//publications/ > > >>Pentax user since 1986, PDMLer since 1998 > > >> > > >>-- > > >>PDML Pentax-Discuss Mail List > > >>PDML@pdml.net > > >>http://pdml.net/mailman/listinfo/pdml_pdml.net > > >> > > > > > > > > > > > > -- > > PDML Pentax-Discuss Mail List > > PDML@pdml.net > > http://pdml.net/mailman/listinfo/pdml_pdml.net > > > > -- > PDML Pentax-Discuss Mail List > PDML@pdml.net > http://pdml.net/mailman/listinfo/pdml_pdml.net -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
