Helios-40 and Helios-40-2 is a modification of the lens Carl Zeiss Jena Biotar 1,5/75. The Helios slightly longer focal length. The optical design is the same — 6 lenses in 4 groups. Helios-40-2 classic planar (Biotar).Draws wonderful portraits on the diaphragm,on the background of the circle of glare.
Transmission coefficient:
Helios-40 — 0,75
Formula color: 10--0--4
Type of enlightenment:
the old issues — chemical, single layer 6)
edition 2012 — multi-7)

The near limit of focusing:
Helios-40 — 1.15 m
Helios-40-2 — 1,15 m or 0.8 m
The limits of the scale diaphragms: 1:1,5–1:22
Number of diaphragm blades: 10

Connections:
lens with the camera:
Helios 40-M39.I'm giving you an M42 adapter ring.Photo taken by me on Sony a7r on open aperture.