A manual-focus lens with a very precise focusing ring. It's circular aperture blades help minimize harsh spikes when stopped down making it a pretty decent lens for astrophotography.  This lens does have quite a bit of chromatic aberration and astigmatism around the edges, but exceptionally sharp at the center. It's generally recommended to stop this lens down a few steps from f2 to f4 or f5.6. Example of stars after photometric color calibration on an APS-C sensor when stopped down to f5.6. [img]https://cdn.astrobin.com/ckeditor-files/25575/2022/b580c06f-9b25-4959-874c-5b3d6c769735.png[/img]