Cosina — Pentax K / Contax-Yashica 135mm f/3.5 short telephoto with built-in hood, 1981
The Cosinon-T 135mm f/3.5 was Cosina's short-telephoto companion to its Cosinon-W wide-angle range, part of the maker's own K-mount catalogue from the early 1980s. It was also produced for Contax/Yashica bayonet cameras and rebadged for European retailers.
Cosina lists the optical formula as four elements in four groups. Surviving examples show a 49mm filter thread, six aperture blades, a minimum focus distance of roughly 1.5m, and a weight in the region of 280 to 310g. A built-in, extendable lens hood is part of the metal barrel.
The built-in hood is the lens's most distinctive feature, since little else in this class routinely offers one. The modest four-element formula keeps the barrel compact and light for a 135mm lens, favouring portability over the wide-open sharpness of faster f/2.8 135mm rivals.
This is a common, inexpensive route into 135mm reach for Pentax K and Contax/Yashica film shooters. Because the hood telescopes, checking that it still slides and locks smoothly is worthwhile, and the narrow rear tube of telephoto designs like this one is a common spot for fungus.