The Helios-40 85 mm f/ 1.5 (Russian: "Гелиос") is a fast lens with a fixed focal length for 35mm cameras with M39 screw mount.
With a special adapter can be attached to modern dSLR and mirrorless cameras.
There are two versions about this lens optical design origin. By one version it was based on Carl Zeiss Jena Biotar 75mm f/1.5 (1938 г., rangefinder system Contax I-III).
Other version rely on fact that first Planar's (fast cinema 35mm lens "Helios-1" 50/2, "Helios-2" 75/2 and "Helios-3" 100/2) were developed by GOI in may 1937y.
So it can be possible that Helios-40 (developed by GOI in 1950) was also fully developed by russian optical specialists.
As it was said before Helios-40 85mm f/1.5 by its optical design is Planar (modification with thickened elements)
In aggregate of its technical data this lens suits better portrait work and art photography with a low DOF.
Helios-40 85mm f/1.5 provides enough sharp but not contrasting image. Colors are slightly faded and have a slightly warm tint.
The main feature of this lens is a special image plasticity (due to MTF curve dip), amazing volume and a nice distinctive bokeh at apertures F1.5-2. At aperture F2.8 half of its charm disappears. Further closing down aperture has no point cause image becomes sharp and dull without any special character.
Multicolored background can be achieved at apertures F1.5-2 with a distinctive radial swirly effect of cicles of confusion. These circles trend to have a "lemon" shape. At this aperture values you also get a noticeable vignetting but this cant be considered as a problem cause it provides additional volume to the image (a.k.a. "tunnel effect").
It is very hard to focus at aperture value F1.5 even with "Lushnikov dandelion" and a special focusing screen (Split-screen + microprizm).
The best focusing results can be achieved by using a LiveView with a great scaling.
Using Helios 40 85mm f/1.5 you have to consider one more feature of this lens - MTF curve dip in the middle between center and edge of a frame.
This results in resolution drop in that area.
- Lens badly resists backligt and lateral light so lens hood is highly recommended
- lens is big and heavy
- focusing ring is located in wrong place that is not comfortable to use. Sometimes it rotates hardly.
Helios 40 85mm f/1.5 differs from Helios 40-2 by these parameters:
- Thread mount (Helios 40-2 has M42, Helios-40 has M39)
- Filter diameter (Helios 40-2 has 67mm, Helios-40 has 66mm)
- Resolution (Helios 40-2 has 36/17 lp/mm, Helios-40 has 32/16 lp/mm)
- Coating (Helios 40-2 has amber-yellow, Helios-40 has a violet color of coating)
- size and weight
There were two modifications of Helios-40 lens. From 1957 to 1965 this lens was being manufactured with a static tripod mount. From 1965 a movable clamp was added to the construction. At present time there is no advantage in having this clamp - owners of this lens deattach it to reduce weight of the lens and to make work with this lens more comfortable during focusing ring use.