Helios's 40-2 85mm f/1.5 — the later Biotar-derived M42 portrait prime famed for swirly bokeh.
The Helios-40-2 85mm f/1.5 is the later version of the Soviet Helios-40 fast portrait prime, based on the Zeiss Biotar formula and produced in M42 and other mounts. The 40-2 designation marks the updated production run, and the design has been remade in modern times, keeping this famous character lens available long after most Soviet optics ceased.
This is a manual-focus M42 screw-mount lens with an 85mm focal length and a bright f/1.5 maximum aperture. Focus and aperture are set by hand and it is a large, heavy all-metal lens in keeping with its fast Biotar-derived design. Exact element counts and weight are not asserted here beyond the verified focal length and aperture.
Like the original it is prized for its swirly rotating bokeh wide open, which whirls background detail around the subject for a dreamy portrait look, along with a soft glow at f/1.5 that sharpens on stopping down. It is chosen deliberately for this signature Biotar-style rendering rather than for corner-to-corner sharpness.
The 40-2 is widely available including newer production, so condition varies from vintage to near-new. Inspect the large elements for haze, fungus and scratches, confirm the aperture blades and preset ring operate cleanly, and check the heavy focus helicoid. Mind the weight and balance when adapting. An M42 adapter makes it a popular character portrait lens on mirrorless.