The Helios 44M lens is one of the most widespread manual lenses in the world. These were produced in the Soviet Union from 1958 to 1992 on a massive scale. The internal design is based on then-popular Zeiss Biotar 58mm f/2 lens. The 58mm focuslength on a APS-C sensor turns into a 87mm FOV equivalent which makes it a really nice medium tele lens. I bought this lens because of 'the swirley bokeh effect', also known as “Cat-eye” effect. This effect gives a special feeling as the background “swirls” around the center focus subject.