On 03/09/06, Jostein Øksne <[EMAIL PROTECTED]> wrote: > 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.
The rear elements will likely be larger, this could contribute to weight however... > 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 These dimensions I can't explain, Id' like to see the front filter thread diameter, the filter on the K lens is 112mm. The 645 lens also has a honking great handle and a far larger tripod mount so I assume they would both cost a deal of weight. > Whatever logic there is to DA lenses having to be the same size as DFA > certainly isn't supported by this line of argument. Given that there is no way to make a lens with a physically smaller aperture than focal length/f-number and the register and lens mount diameter remain the same it's not likely that they would be smaller for any tele designs. -- 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 [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
