Recently pulled out the old Pentax A50 f2.8 macro for a few shots of autumn leaves in the back yard.
This lens performs wonderfully on the new Pentax K-1. Though not a “true macro” with a reproduction of 1:2, I find the scale adequate and the IQ superb; plus it is such a joy to use.
I can see why vintage Pentax glass was noted for it’s quality, the colors are brilliant and the IQ is sharp for the area of focus. Bokeh is pleasantly pleasing also. This doesn’t seem to change on the new digital sensors either.
In fact, I find their performance is equal to or better than the newer digitally enhanced lenses.