Originally posted by WPRESTO Do you know if they are all the same optical formula? If there is one that's different, I would immediately suspect the original tele-Takumar. Among those early lenses I think that the 200mm f5.6 is also regarded as a very good lens.
I have a Tele-takumar 200mm f5.6 and its a great lens, sharp across the range of focal distances, including at infinity and wide open. I have an original Pentax metal screw-in lens hood.
I also recently picked up an Auto-Takumar 55mm f2.2 with a cocking lever, and that's also extremely sharp lens. It's a 46mm thread, so I have adapted a 49mm screw-in hood.
For the old Taks, I almost always use as long a hood as will avoid vignetting, that partly compensates for the older coatings.