Photax — budget manual-focus 135mm f/2.8 short telephoto, M42 and bayonet SLR fittings
Photax was a UK house brand of the 1970s-1980s, used by photographic retailers to sell budget Japanese-made optics alongside own-label cameras and accessories. The 135mm f/2.8 was sold as a short telephoto companion to a 50mm kit lens for portrait and general use.
Focus and aperture are set by hand via knurled metal rings, with a click-stopped iris diaphragm typical of manual optics of the era. It was offered in universal M42 screw mount and bayonet versions fitting major SLR systems of the time. Element count, coating, weight and filter thread are unconfirmed and omitted rather than guessed.
A budget 135mm f/2.8 of this class typically gives moderate contrast and gentle background blur rather than the strong subject separation of faster first-party portrait lenses, with corner softness and some flare wide open. Stopped down to f/5.6-f/8 it becomes a usable, compact telephoto.
Examples circulate mainly through camera fairs and online auctions rather than specialist dealers, priced low given the house-brand origin. Check the aperture blades move cleanly, mount threads or bayonet lugs are undamaged, and glass is free of fungus or haze before adapting to a mirrorless body.