So, a few observations on the Tamron Adaptall (1st gen) 70-150mm f/3.5. Here's the PF entry on it (mine was the non-macro version):
Tamron Adaptall 70-150mm f3.5/3.8, CZ715, CZ150, QZ150M Lens Reviews - Tamron Adaptall Lenses - Pentax Lens Review Database
- The lens handles reasonably well, despite its length (about 110mm, or 4-1/2") and minimum focusing distance (1.5m - THAT bothered me for a while). My copy focused smoothly, although the helicoid turns about 190 degrees, and that feels like a long throw when you're in the zone. Items popped into focus without much issue, and the long throw made fine adjustments easy.
- No complaints with color rendition, although things felt a bit cold and flat straight out of camera - I can't pinpoint it any more than that. I usually punched the vibrance, saturation and clarity settings up a tad in Lightroom pretty much as a general practice.
- from f/3.5 to f/8, the lens shows its "Hyde" side - very soft wide open, with paintery, glowy bokeh. I found this really frustrating, but in retrospect it did result in some interesting rendering, if you're looking for that kind of thing:
at f/4.5, things got a bit better, but still glowy and soft. This shot made Explore for a few hours, so I can't complain:
f/8 was - ugh - just mediocre. Average sharpness, and by then most of the glowy bokeh had disappeared. At that point, I was ready to give up.
But at f/11 and above - rather abruptly, and shockingly - the "Jekyll" side of the lens took hold: impressive sharpness and rendering - rivaling some of the best vintage lenses I've used:
That sharpness held, more or less, all the way up to f/22, but f/11 and f/13 were the sweet spots.
The other thing I discovered - and ended up loving - was the flare, which began showing up if the sun was, say 20-30 degrees off to the side. It wasn't pretty, necessarily, by itself - but when I threw it into HDR Efex Pro 2 and began to play, i ended up with some stuff I really liked.
I may pull this lens out, from time to time, just to do this.