Vivitar's 24mm f/2 — a fast third-party M42 wide-angle prime for landscape and street.
The Vivitar 24mm f/2 is a fast wide-angle prime sold under the Vivitar brand in M42 mount. Vivitar was a marketing house that had lenses built by various Japanese makers, so build and optics can vary by production batch, but this was a fast 24mm in their screw-mount range.
This is a manual-focus M42 screw-mount lens with a 24mm focal length and a bright f/2 maximum aperture. Focus and aperture are set by hand on the barrel, with an automatic diaphragm. It is an all-metal wide-angle. As with Vivitar-branded lenses the maker varied, and detailed element figures are not asserted here beyond the verified focal length and aperture.
A fast 24mm gives a wide rectilinear view usable in lower light, suited to landscapes, architecture, interiors and street work, with some subject separation from the f/2 aperture. Vivitar wide-angles of this era render acceptably stopped down, and the fast aperture makes this a versatile wide for varied conditions.
Used copies vary in quality with the actual maker, so inspect each on its merits. Check for haze, fungus and cleaning marks, confirm the aperture blades are clean and oil-free, and check the aperture-ring and focus feel. Verify the M42 mount before purchase. An M42 adapter allows fast wide-angle use on mirrorless cameras.