This is vintage lens made in the former Soviet Union ( USSR ). HELIOS-44M f2/58mm - one of the most common lenses of the Helios-44 series.
Petzval Helios 44M is a modified version of Helios 44M to create the effect seen in Petzval lenses. Namely, artistic blurring of the center of the image, which requires a little digital sharpening.
The lens produces a bokeh effect similar to a petzval with a fully open aperture and maximum defocusing of the background with the obligatory backlight. Example: the distance to the subject (portrait) is 1.5 m, the distance to the background (flowers) is 3.5 m. The background (flowers) is illuminated by lanterns. . Aperture f=2.
As a result, there is a portrait in the center of the frame, and swirling bokeh at the edges of the frame. To enhance sharpness, little digital processing is required
The lens is designed to work on SLR cameras with a flange distance of at least 55mm, and on mirrorless cameras with an extended adapter that increases the flange distance to 55mm.
This lens does not focus to infinity, but is only used for portrait or artistic photography.