There are two 165mm lenses, an f/4 with leaf shutter, and an f/2.8 without. Earlier on, there was a leaf shutter 90mm f/2.8, and the current no-shutter 90/2.8 as well.
A clue to earlier lenses is the Takumar name, which was given up sometime before the camera name change from Pentax 6x7 to Pentax 67. After Takumar, the lenses were called SMC Pentax 6x7. Newer lenses bear the Pentax-67 name.
Some lenses had optical differences between versions. The earliest 55mm was an f/3.5 Takumar with a very large front element, IIRC it used 100mm filters. The big Pentax 55mm lenses got a reputation for fine performance. About 1979 a new f/4 "Pentax 6x7" 55mm was introduced that used 77mm filters... much different in appearance and optics. The third and last version was "Pentax 67" 55mm f/4 which looked very similar to the previous model, but went from 9 elements in 8 groups to 8 elements in 7 groups. These are all excellent lenses, but it's useful to be aware of the different versions.
The 200mm f/4 also changed quite a bit... The S-M-C Takumar 6X7 200mm f/4 of 1971 is the same optically as the original Super Takumar 6X7 200mm f/4 of 1969 with 4 element design. Was redesigned in 1986 for lighter weight, a 5th element, closer focus, f/32, and filter size 77mm instead of 67mm... now "SMC Pentax 67".
There were also three different 75mm lenses... a regular 75mm f/4.5, and a larger manual-diaphragm Shift 75/4.5. Then one of the last lenses added to the 67 system (2001) was a smaller lighter Aspheric 75mm f/2.8 SMC Pentax 67 AL.
There are a couple of macro lenses to be aware of... First the original 135mm f/4.0 SMC Macro-Takumar 6x7 that had changes in the name and minor cosmetic changes over the years, easy to find on the market. With 5/3 construction it could well be a Heliar formula, like the small-format Pentax f/4 100mm macro. A bit confusingly, there's a later (March 1998) 100mm f/4.0 SMCP-67 Macro to replace the 135mm. This one has a front-screw-in "Life Size Adapter" allowing 1:1 magnification. It is a 6 element 4 group lens (obviously not a Heliar), and the Adapter is 3 elements.
There have been a lot of interesting lenses in the 6x7/67 lineup, as it's quite a rich system starting from 1969 but I think most didn't have optical changes (other than coating changes) across the various name and cosmetic changes.
Last edited by Doug : 06-08-2010 at 18:04.