The Helios-77M-4 50 mm f/ 1.8 МС (Russian: "Гелиос") is a fast standard multicoating lens. Was used as a KIT lens with a Zenit camera.
Was being manufactured at "Upiter" factory located in Valday town and at Optic and Mechanical factory in Vologda town. Originally lens was developed at KMZ factory. This lens differs from Helios-44M-4 with its faster speed and wider angle of view. Also it is more compact and has a higher resolution.
Real focal length - 52mm.
Angle of view: 44 degrees.
Filter diameter: 64mm.
Resolution (center/edge): 45/25 lp/mm
MC Helios-77M-4 50 mm f/ 1.8 has enough good optic characteristics even for modern requirements. Being wide-open it is sharp and has a good bokeh. Best contrast can be achieved if lens closed to F4 and further.
This lens has problems working with side and backlight and multicoating doesn't help much. I recommend using it with a hood.