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 Øksne 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 Øksne <[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
