Specification of LOMO OKS 2-100-2 optical block

Many operators use OKS1-100-1 (2/100mm) lens. But this lens has not very high image quality. That is why it is recommended to use OKS2-100-1 lens (2.8/100mm) purposed for 70mm film but having different focusing mount and smaller front element. Such lens was named OKS2-100-2. It has higher image quality and is used in anamorphic block 35BAS22-2 as well.

Unfortunately, this lens version is relatively rare. I had only couple of them.

Manufacturer		NPO "EKRAN"
Lens system		-
Focal length	f'	99.7 mm
Angle of view	2ω'	15°30'
Effective relative aperture	f:n_э	1:3.2
Lens length	Σd	75.9 mm
Front focal length	S	-39.4 mm
Back focal length	S'	57.8 mm
Flange focal distance	Z	90.5 mm
Block length	B	85.5 mm
Block max. diameter	D	54 mm
Rear diameter	D'	38 mm
Front element diameter	d₁	37.8 mm
Rear element diameter	d₂	28.3 mm
Mount thread		-
Distance from rear end of the housing to the focal plane	l	51.3 mm
Aperture blades quantity		?
Frame size		16x22 mm
Weight		320 g