This is another in a series of field tests on P67 lenses.This lens seems to be contraversial as to sharpness among its users. After using it for ten years, I will give some opinions. The optical cross section shows that the design is a semi-symmetrical, partially air spaced, Double Gauss type. The Takumar and Pentax 105s are the same optically even though they look quite different externally. This is a proven, old design that has long been used in 35mm SLRs, especially for fast, normal lenses. This lens performs very well in macro situations even when stopped down to f/22. I feel that the 105 is sharper at f/22 for macros than at infinity. Sharpest stop (non macro)- f/11... Slightly soft at f/2.4, 4.0, 22. The 105 is fast enough to hand hold given the right film is used. It can be used for group portraiture, landscapes, macros, travel and even weddings in a pinch. Overall, a great lens for the money. It is easily Pentax's best value in the P67 line. SR

-- Steve Rasmussen (srasmuss@flash.net), December 10, 1998

Answers

Frank: Our opinions are not as different as they may first seem. My 105 will also make good 16x20 prints of landscapes at f/22 through f/5.6. It's just a bit sharper at f/22 for macro work. I use the Helicoid and Ilfochrome printing. I don't know why yours is not sharp for macro work. This type of lens has been used quite a bit for copy work and should be a natural for macros.

-- Steve Rasmussen (srasmuss@flash.net), December 13, 1998.

Gene, I have the Takumar and suspect that Asahi Optical has a quality assurance problem with the 105mm since this camera has become so popular in the last five years. The 105 has got to be the most produced lens they make and I feel their manufacturing variability has increased. Mine will show pollen grains on flowers as points, shot at .5x mag using a helicoid and f/22. Sharp 16x20 prints can be made of macro or infinity work even at f/22. Not positive why some 105s vary so much. SR

-- Steve Rasmussen (srasmuss@flash.net), January 15, 1999.

Steve,

I guess this is what causes the controversy: your experience with the lens for macro work vs at infinity is quite the opposite of mine.

I once tried to make enlarged internegs from some slides with the 105 on extension and the results were unusable. I used open flash at f/11 for exposures and did numerous variations of exposure - all were bad. I ended up using a Takumar 50mm Macro (for 35mm cameras) under the same conditions with much better results.

Some of my best landscape shots with the 105 have been printed at 16x20 with beautiful results.

Regards,

Frank

-- Frank Kolwicz (bb389@lafn.org), December 12, 1998.

My experience with the 105mm is different. Mine was purchased new two years ago. At f16 and f22 the images get unacceptablely soft. The pentax booklet warns that pix will not be the best at the smallest apertures. My lens tests confirm this fact. Have't used it in "macro". I assume you are talking aobut at the closest focusing distance. I have the new 55mm and it is so fantaastic, that I keep on the camera most of the time. The 105 does't get much use.

-- Gene Crumpler (nikonguy@emji.net), January 15, 1999.