I tend to think that Pentax will produce only DA lenses. But I also still feel that the size difference between FDA and DA at longer focal lengths could be minimal. Paul On Sep 3, 2006, at 5:02 AM, Jostein Øksne 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=categoryNav > igation > > 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 > -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net
