Osawa 24-43mm f3.5-4.5
Osawa produced lenses until 1984. Some of their lenses were quite good while others were quite average. It's trial and error to find a good one.
This lens is a bit too complicated for its own good. Focus throw is quite short. Focus and Zoom rings are heavily dampened, too heavily dampened. The aperture ring is also dampened too heavily. Adjustments on this camera are slow to make. The lens has a macro mode which engages by poulling the zoom ring down at 43mm. This procedure is actually easy to do. After testing the lens I understand why macro mode is friendly to use.
Image quality outside of macro mode is average. It's soft at f3.5 and doesn't tighten until f8. Contrast is quite low thru the entire zoom range and at all apertures. Fringing is noticeable at f3.5- thru f5.6 and color rendition is flat. There is noticeable vignetting at 24mm. They seemed to mfg this lens to be average at all settings, except macro.
In macro mode the lens comes into its own. At f3.5 it is soft but it tightens up at f4 and actually gets sharp at f5.6. Contrast is also much better in macro mode. At f11 it is quite sharp, but bokeh is a bit distracting.
When Sun Optical produced their 24-40mm, it was not only the first of its kind, but it performed reasonably well, too. Many manufacturers tried to copy that lens and failed miserably. The Osawa 24-43mm seems to be one of those failures.