Carl Zeiss Jena's Exakta 135 — the Sonnar 135mm f/4 medium tele with firm contrast.
The Carl Zeiss Jena Sonnar 135mm f/4 is a medium-telephoto prime from Jena, offered in the Exakta bayonet as the higher-grade alternative to the simpler Triotar. The Sonnar name marks a more corrected multi-element design that traded the triplet's simplicity for better contrast and correction. It sat in the Exakta line as the mainstream quality 135mm for portrait and general long-lens work.
This is a manual-focus Exakta-mount lens with a 135mm focal length and a maximum aperture of f/4. It uses a Sonnar-type optical layout, a more complex multi-element design than the Triotar. The aperture is set on the barrel and coupled through the Exakta internal lever on supporting bodies. Weight, filter thread and element count are left out here where they cannot be confirmed for the specific Exakta variant.
The Sonnar 135mm f/4 renders with firmer contrast and cleaner correction than the Triotar, giving good central sharpness stopped down while keeping smooth out-of-focus areas. The 135mm focal length is a natural portrait length, placing subjects at a flattering working distance, and it doubles for travel detail and general telephoto use. Its rendering is classical Zeiss Jena rather than modern-clinical.
Exakta Sonnar 135mm lenses are moderately common and reasonably priced for the quality. Inspect the glass for haze, fungus and separation, and confirm the aperture blades are dry and click properly. Check the coatings for cleaning marks and test the long focus helicoid for smooth travel. Adapted to mirrorless with an Exakta adapter it makes a capable, affordable vintage 135mm portrait lens.