The OKS7-28-1 lens has extended back focal length of 32 mm. Optical construction is complex system consisting of 9 elements grouped into 7 components. Image quality corresponds to early OKS4-28-1 lens, but OKS7-28-1 lens has longer back focal length.

Manufacturer NPO "EKRAN"
Lens system -
Focal length
f'28.0 mm
Angle of view2ω'51°50'
Effective relative aperturef:nэ1:2.3
Lens lengthΣd43.3 mm
Front focal lengthS-
Back focal lengthS'31.5 mm
Flange focal distanceZ41 mm
Block lengthB45 mm
Block max. diameterD45 mm
Rear diameterD'SpM 33x0.75
Front element diameterd131 mm
Rear element diameterd218.5 mm
Mount thread SpM33x0.75 cl 2a
Distance from rear end of the housing
to the focal plane
l32.5 mm
Aperture blades quantity 12 ?
Frame size 16x22 mm
Weight 130 g