Be sure that the lens has an A(Auto) and M(manual) switch.
Don´t buy an electric version, e.g. the Zeiss Pancolar 50mm 1,8 exists in 2 versions.
The pins of the electric version could(not all) snag with the 4 srews of your camera mount. I have made this experience.
I have a Tokina 17mm 3,5 ,20mm 2.8(!) Zeiss Jena Flektogon (expensive), a 28 mm Revuenon, the Pancolar and a Zeiss Jena Tessar, a Pentacon 135 mm 2,8.
They all are sharp, but produce different colors. The wide angle lenses(which ist normal in 16mm) are of course more expensive.
I wouldn´t widen to ultra16 but super16.