The B+W 37mm Dark Red SC 091 Filter can be used to increase image contrast when photographing using a film camera system with black-and-white film installed.

This filter's effect corresponds to that of a Wratten 29 filter. Wavelengths of visible light that are apparent as green and blue colors to the human eye are suppressed, while visible light associated with orange and red colors are able to more easily pass though the B+W 37mm Dark Red SC 091 Filter and into the lens it is mounted in front of. When photographing with this filter along with black-and-white film, green to blue-colored subjects within a scene are reproduced in extremely dark shades of grey than if a filter was not used. Simultaneously, orange to red subjects are rendered in extremely light shades of grey.

When applied to black-and-white photography, the increased contrast provided by the B+W 37mm Dark Red SC 091 Filter can result in extremely dark skies while helping to maximize the definition of clouds. Shades of green among foliage can become sharply differentiated from neighboring shades of orange or red, while light skin tones can be rendered as white or near-white. Additionally, this filter can also minimize the presence of haze caused by the bluish cast of daylight.

To prevent internal ghosting and reflections, each glass surface includes one layer of anti-reflection coating. B+W filters are constructed from Schott glass for increased optical clarity. This filter features an F-Pro brass filter ring for durability as well as jamming prevention.