This 37mm #630/091 Dark Red MRC Basic Filter from B+W can be used to increase image contrast using black-and-white film. When using this filter, blue skies are reproduced in dramatically darker shades of gray than if a filter was not used. Simultaneously, red to light yellow subjects are rendered in lighter shades of gray. Landscape and architectural photos show an increased, almost graphic contrast, while a cloudy sky may already appear dramatic.