I finally got around to deglassing a Takumar 2X teleconverter (needed nothing more than a paper clip!), and so had a chance to test with a A50/2.0 lens for some macro shots. At this combination at closest focus the magnification is about 0.65X. I wondered whether this lens would be good enough once stopped down to f8 or thereabouts, and it seems to have done fairly well. Conditions were very windy, so focus was hit and miss (or more accurately spray and pray) as I shot in burst mode.
