The first thing you'll notice about this lens is the size of the front element. It's huge. This lens was also made in later years as the 150mm SMC Takumar. As far as I can tell, the lens was made from the beginning to around 1983. The lens has a metal barrel with metal focusing ring. It is fairly heavy for its size. Performance: The DOF scale seems to be off by one stop. If you have the aperture at f/22, the DOF scale needs to be set at f/16. It does well with extension tubes for closeup work and is fairly sharp, even though it could use an f/32 stop. The sharpness at f/5.6 is excellent. At f/2.8 it is only slightly soft, as is f/22. I have never seen the cross section for this lens but it is most likely a six element Double Gauss design, similar to the 105mm. As a portrait lens, it a bit too short for me. For group shots it is OK. It will not do tight head shots without an extension. The angle of view(around 33 degrees) seems to do quite well for certain landscapes. Overall, a nice lens but needs closer focusing and f/32 depth. SR

-- Steve Rasmussen (srasmuss@flash.net), October 19, 1999

Answers

Thanks Patrick. We can make this forum anything we want; not just Q & A. SR

-- Steve Rasmussen (srasmuss@flash.net), October 22, 1999.

After using this lens more extensively since my field test, I have several other conclusions to piont out. It is sharper than I first realized at f/2.8. It could easily be Pentax's sharpest lens at full aperture. After much more macro work with a helicoid, I have concluded that other lenses are better suited for macro work than the 150. Its DOF is just too narrow. One secret to hand holding this lens at 1/30 sec is to hold the end of the lens with the fingers so that they form a circle around the very front part. This works surprisingly well! SR

-- Steve Rasmussen (srasmuss@flash.net), December 06, 1999.

Leendert, thanks for the expanation of the cross sections for the 150 and 200 Takumar. I was surprised to hear the 150 was a five element. The design is similar to the 200 Takumar(which I do have a cross section on)and is called a modified triplet. It is rare to see this design in a speed of 2.8. Designers usually go with the Double Gauss. The proof in the 150's five element design is in its performance. SR

-- Steve Rasmussen (srasmuss@flash.net), February 13, 2000.

I finally figured out what design the 200mm Takumar is. It is called an Ernostar-Sonnar. A German based design just like the Ernostar and the Sonnar. SR

-- Steve Rasmussen (srasmuss@flash.net), February 16, 2000.

After seeing the actual cross section of the 150mm it is obvious to me now that this design is not a modified triplet but a five element Double Gauss, not much different from the 90, 105 and 165, f/2.8.

-- Steve Rasmussen (srasmuss@flash.net), November 11, 2001.

Thanks Steve, I don't tend to respond to your field tests when I read them but I think we need to make sure you understand we all appreciate the efforts that go into it. Keep it up!

-- Patrick Drennon (sierraengineering@worldnet.att.net), October 20, 1999.

Hi Steve, I found drawings of optical cross-sections of some older Pentax lenses in Dutch "FOTO" of june 1971. The lenses of interest: 55mm/3.5, 2.8/150, 4/200 (old). Since I have no scanner, I can only describe the cross-sections to you. 150/2.8: 5 elements, 5 groups. 3 in front, 2 in back. 2 positve, convex-concave elements in front close together, then an bigger air space and then a thicker negative plan-concave element, flat side to the front. Then diafragm, then 2 positive lenses close together, the first concave-convex, the last plan-convex, both elements with convex surface pointed to the camera. 200/4: 4 elements, 4 groups. 3 in front, 1 behind diaphragm. Like 150mm first 2 positive convex-concave in front close together, then a bigger air space followed by negative plan-concave element. Behind the diaphragm a single convex-concave element, concave surface facing the filmplane ( as opposed to the 150). Pff... Doesn't a picture say more than a thousand words? Greetings, Leendert.

-- Leendert van de Klippe (leenvdklippe@hetnet.nl), February 13, 2000.