If it's a SMC Takumar, (and I would expect it is), when that lens is mounted on a Spotmatic F or ES there is a groove that keeps that pin from being pressed into the lens and stops the lens from being set from Auto to Manual, which would confuse the meter readings. On any other Pentax M42 body the pin is depressed which allows the lens auto manual switch to move freely.
At 10:56 AM 9/12/2002 -0700, you wrote: >Thanks, John. > >It all helps. Now I'm faced with selling a couple of my stop-down >aperture lenses and replacing with full-aperture metering lenses. I >bought a couple when I was 'unaware.' <g> >I really hate getting rid of my Super Takumar 135mm f/3.5 M-42 mount. >It's so smooth and small, and almost brand new! If there's an SMC >Takumar version of the same lens, that has the aperture lever, either >M-42 or K-mount I'll buy it! > >I have both a Pentax MG and a Spotty F, so I can use either lens. I >suppose I should shoot for an M-42 version, because I can put a >bayonet adapter on the M-42, but not vise-versa! >I do have another 135, an f/2.5 version, but it's so much bigger and >heavier than the littler f/3.5 version... > >All of your info helps a lot in increasing my understanding of the >various Pentax lenses. > >One question left...there's a _tiny_ spring loaded pin on the rear >_mounting_ face of my M-42 lenses. It's located about 1/4" CCW from >the solid machined stop on the aperture ring on the rear, but the pin >itself is on the mounting face. >What is it? > >Keith Whaley > >John Coyle wrote: > > > > Hi Keith: > > Here's my understanding of the various combinations of Takumar, SMC > > etc: > > Takumar was the original name for the non-auto diaphragm lenses of the > > 1950's - 60's. Some of these were pre-set diaphragm lenses, with an > > additional control ring. You focussed these at full aperture, then > > stopped them down for exposure (and for metering with the Spotmatic and > > later). > > Auto-Takumars were introduced with semi-automatic diaphragms, where you > > opened up the aperture for focussing, and the camera closed it on > > pressing the shutter release > > Super-Takumars were introduced with the fully auto-diaphragm mechanism > > when the Spotmatics, SV's and S1a's were produced, beginning about > > 1963-4. Lenses of 200mm and over continued to be produced with no > > automatic diaphragm, and remained designated as Takumar or > > Tele-Takumar, whether pre-set or manual diaphragm. > > (Source: 'Asahi Pentax Guide', Focal Press, tenth edition, August > > 1967) > > > > Super-Takumar, then, does not necessarily refer to the coating used. > > > > Super-Multi-Coated coatings were introduced in 1971, and the lenses > > were Bagdad "Super-Multi-Coated" in full. Pentax lenses were coated > > prior to this, but part of the marketing of the SMC was that it was > > more efficient for less thickness of coating - test reports at the time > > said it blew away competitive coatings, and IIRC, had been either > > jointly developed with, or licensed to, Carl Zeiss, who designated it > > as T* coatings, or something similar. These seven-layer coatings, > > according to the LX brochure, reduced the loss of transmitted light to > > 0.2%, compared with 1-2% for conventional coatings. > > > > It was with the change of mount to the bayonet that Pentax lens were > > designated "Pentax" rather than "Takumar", and the SMC abbreviation > > replaced the full text. I have a brochure for the original "K" series > > release in which all of the new lenses are named "SMC Pentax" with the > > suffix "Shift", "Macro", etc., where appropriate. > > > > The generally physically smaller lens range introduced for the M series > > was designated "SMC Pentax-M". > > > > The LX brochure lists both SMC Pentax-M and SMC Pentax lenses, and I am > > not sure whether the non-M ones are new introductions or a continuation > > of the K series: for example the SMC Pentax 15/3.5 appears in both > > brochures, but the SMC Pentax 30/2.8 only appears in the LX list > > > > The "Takumar Bayonet" range, introduced as a budget range in the later > > '80's, did not carry the "SMC" tag at all, and, while my example of the > > 28/2.8 is optically good, it undoubtedly would be prone to more flare > > than the M-series, which looks like a totally different design. > > > > HTH > > > > John Coyle > > Nicholas John Consultants > > Brisbane, Australia
