Soviet Orange Filter OS-12. Diameter 40.5 mm with 0.5 mm pitch.

Specifications and Parameters:

This filter is manufactured by the Lytkarino Optical Glass Plant (LZOS).

Marking: OS-12 (Light Orange, spectral number 12).

Thread Size: Diameter 40.5 mm with 0.5 mm pitch (marked on the frame: 40.5x0.5).

Compatibility: Fits many classic Soviet lenses, such as the Jupiter-8, Jupiter-11, Jupiter-12, Industar-26M, Industar-61 L/D, and others with similar threads.

Package Includes: The filter comes in its original transparent plastic case.

Purpose and Application: This filter is primarily intended for black-and-white analog (film) photography. It performs the following functions:

Contrast Enhancement: Significantly blocks blue-green light, making blue skies appear significantly darker and more dramatic, while white clouds appear sharp and vibrant.

Haze Reduction: Helps minimize haze when photographing distant landscapes and architecture.

Portrait Photography: Gives skin a more even tone, effectively masking or completely "lightening" (making invisible) freckles and age spots on black-and-white film. If you plan to use it, keep in mind that the dense orange glass absorbs light, so exposure compensation will be required during shooting (usually this filter requires an increase in exposure of approximately 2 stops (4x).