Tefnon was a third-party lens brand sold through UK and European photographic retailers, including Dixons, from the late 1970s into the 1980s, badging lenses manufactured by Japanese OEM optical houses for buyers wanting affordable wide-angle options for their SLRs.
The 28mm f/2.8 is a moderate wide-angle prime of conventional retrofocus construction for the period, sold across a wide range of mounts including M42, Pentax K, Canon FD, Minolta MD, Olympus OM and Nikon F to match whichever camera a customer owned. Build is mostly metal with a rubberised focus grip typical of the brand.
Sharpness is central-weighted, softening toward the corners wide open, with contrast that is workable but noticeably lower than contemporary first-party 28mm lenses. It is a lens valued today mainly for its low cost of entry into manual-focus wide-angle shooting rather than for optical character.
Tefnon lenses are common and cheap on the secondhand market, frequently found loose in dealer bargain bins. Buyers should check the aperture ring detents for wear and confirm the front element is free of the light haze that affects many lenses of this brand and era.