The weekend 9-11 February, I borrowed a 645-A 120mm f/4 macro lens and a converter for 35mm system. My goal was to test this combo, and compare it with the gear that I already use for macro work; and with approximately the same focal width. This is NOT an accurate test of MTF-resolutions or alikes, but simply an attempt to see performance in real life.
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The 645-A 120mm f/4 macro lens outperformed the other lenses tested at 1:1. I doubt, however, that it would be as good as a 35mm-designed true macro lens (eg. the FA 100mm f/2.8 macro).
At "portrait" distance, ca. 2.1-2.5m, the performance was roughly equal among the lenses.
The 645-A became a clear looser at infinity. Its sharpness at f/4 was particularly poor.