The Carl Zeiss Jena Sonnar 135 mm f/4 is a portrait prime lens for 35 mm DSLR Exakta, Praktina system and M42 screw mount cameras.
The first M42 version can boast a silver-colored lens body. The lens features the focal length scale with centimeter marks (13.5 cm). The lens glass elements are not coated. The lens is remarkable for its solid build. The aperture functions perfectly well even today. The lens is very sensitive to front lighting exposure. The hood may be helpful, but it is not capable of fully improving the situation.
The second version of the lens features a coated front element. This modification can boast a new body design and smoother focus ring travel. The word “Sonnar” in its designation was replaced with the letter S. Focal length is measured in millimeters. Its aperture functions a bit worse. Today the majority (if not all) of these lenses have issues with grease hardening on aperture blades, which partially or completely immobilizes the aperture. The lens was manufactured in the time of black-and-white photography, and when used on modern digital cameras it produces somewhat cold colors.