Hello !
I received from someone a few years ago a couple of M42 Takumars. The 35mm f2 Super Takumar and the 150mm f4 S-M-C. I've loved using the 150- it's a fantastic lens. The 35 hits the mirror on my 5Dii and is yellow. Both are relatively easy fixes. As we all know- these lenses are precision machined and jewel-like. So I bought a 28mm f3.5, a pristine 135mm f2.5 (v2, 6 elements) and a 200mm f4 Super Tak. I did have trouble finding the v2 135mm f2.5 at the right price in the right condition, so at first I bought a Nikkor 135mm f2.8 non Ai and sold it almost immediately. It was not for me: soft wide open, with an "agricultural" feel. It did work well stopped down. It is a very rugged lens that can take a beating- I think much of Nikon's reputation is owed to that.
To afford these I've been selling off camera equipment that I haven't been using. That included my mother's Pentax MX with some lenses, a Minolta SRT with lenses and cases, and so on. I was able to sell the MX pretty easily, along with some of the Minolta gear, but my Pentax M 50mm f1.7 didn't sell, nor the M 135mm f3.5. I knew I could modify them to suit my 5Dii, but already had those focal lengths and was not interested. With little to lose, I decided to experiment. I removed the plastic ring at the back, shaved the fin shaped protrusion on it, and snipped the aperture tab to sit flush. Put the ring back on and- a perfect fit on the Canon. The 50 is a fine lens, but I am really surprised with the M 135 ! It really does rival the v2 M42 Takumar 135 f2.5. They are very close in performance. The M lens is much easier to handle and seems to focus much faster. I have focus confirmation chipped adapters on both. If I don't have enough of a reason to keep the much larger M42 135 I will sell it, despite its beauty as an object.
One thing I should note to anyone buying or selling these- or any lenses is to not pack them into old hard cases without at least bagging them. Two of my Takumars (28mm and 200mm) arrived covered with dust from decaying foam and board in their cases. It is incredibly disappointing to find a lens that way ! I was able to clean them successfully and they work perfectly.
I want to thank this forum - and the reviews here for providing me with some insight into the world of Pentax lenses. In searching for information on lenses- of any kind- the reviews here were almost always first in the search results. Well done !