Originally posted by kypfer I wonder how well related these "modern" fixed-mount lenses are to the Adaptall-2 originals. I had one of the #71A's when they were new (mid to late '80's, at a guess) and replaced it with a #171A when they became available. The first was a vari-focal design, in that the focus changed as the lens was zoomed, and it only had a minimum focus of about 6ft, as I remember. The later lens was (is) far more user-friendly, which stayed in focus as you zoomed and with a minimum focus of 3ft. The first had a rotating front element, so the lens hood was fairly minimal, but the later had a "petal" hood which was far more efficient. My example unfortunately developed haze/fungus deep in the internals and was retired only a couple of years ago
According to Tamron they started developing the 28-200 in the late 80ies and the first one to appear on the market was the 71x, which was - to the best of my knowledge - the only generation, that appeared as Adpatall-2 (71A) and fixed mount (71D).
Originally posted by kypfer .... and replaced it with a #171A when they became available. ... with a minimum focus of 3ft. ....
That is exactly what Tamron mentions as the main advantage of the 171D in their history of 28-200s. BTW, the 171D is the technical basis of the smc Pentax-FA 1:3.8-5.6 28-200mm -IF&AL-. Actually they seem to be identical apart from the exterior "Pentax-look" and the SMC coating of course.
I once compared the optical performance of the 71D and the Pentax FA 28-200 (~Tamron 171D) and noticed a slight advantage of the Pentax. However, today on the K-1 it is simply not good enough to provide satisfactory results.