Tamron 70-210mm f4-5.6 Adaptall
This adaptall lens was made at a time when plastic was being used to cut costs by most lens makers. It is very light, not well made and quite clunky. The focus/zoom ring is not dampened, much like an AF lens' focusing ring. Focusing is difficult to nail and almost impossible to maintain. It's a shame because the optics aren't bad.
I took some quick pics fom the window. I shook a little on some of the pics. It won't be noticeable in these samples.
Sharpness is acceptable. Actually, it is better than many lenses which cost much more.
Contrast is a little low at 210mm.
Color rendition and saturation is a bit flat but not bad.
There is noticeable fringing in high contrast scenes. but you may not see it in standard prints.
For $20 it is a good usable lens optically. The cheap feel may be a turn off for you as it is for me. However, it is ver light and relatively, so you may find it handy on a mirrorless body.