Manual focus "only" lenses - Adaptall2
I do appreciate TAMRON ceasing their support of their own Adaptall2 prduct line on SONY, Canon, Nikon and Pentax camera bodies, by discontinuing the Adaptall2 adapter collar. "Appreciate" in the sense that these lenses simply cannot provide a sharp enough resolution without the aid of an addition MF focusing screen. I believe our eyes (perhaps just mine ... and I felt I was pretty good at that) just are not that great at picking up the visual cues better than the digital sensor can.
Even with the MF focusing screen, it is a still struggle. Also, the these older lenses do NOT have the coatings and treatments necessary to be competative with today's standards in lenses. Color aberration (CA) and purple fringe run amok with them and based on comparative shots that I have done ... well, let's just say that I have gone ahead and methodically replaced ALL of my Adaptall2 lenses (135, 200, 70-210, 200-500), in one way or another, with digital AF types ... basically all of them with TAMRON, except for the SONY CZ 135mm f/1.8.
I still keep these manual lenses for use on the film bodies, but when it comes to use on the digital ... overall, it's just been a bust. :( C'est la vie!
As far as the MF focusing screen goes, it has been an excellent tool, for use with AF glass, when I could not obtain focus "automagically", such as shooting through weeds, tree branches or other interference, like screens and windows. If you routinely find your self in manual focus, or using DMF, I highly recommend having it, but you need to be aware that it offers small challenges, too, when it gets darker. :cool: