Good contrast, a defining characteristic of black-and-white, can be quickly washed away because the tonal values become too similar once stripped of color. Red and green offer nearly equal luminance in black-and-white, for instance. Optical filters alter these tones prior to the desaturation process, building contrast between monochromatic objects at the same time that they enhance black-and-white tones and hues.
The basic rule in black-and-white is that a filter will lighten its own range of colors while darkening complementary colors. The stronger the filter’s hue, the more intense the results, while lighter color filters are often used for more subtle corrections. Pricing varies depending on the size of the filter, which must match the front diameter of your lens if it’s a screw-in optical filter. There are also larger square optical filters that affix to the front of your lens through a mount. These are compatible with most lenses, but can be more expensive than screw-in filters.
A red filter limits blue and green wavelengths while allowing red colors to pass through for dramatically enhanced contrast and texture. Useful for enhancing the greens and blues of natural landscapes, the heightened contrast helps to separate less impacted areas of your image, like white clouds, which will stand out against blue skies that are made very dark, or bright flowers, which will be more pronounced when surrounded by green foliage. The results are extreme so the effects can be very surreal, and sometimes there will be too much contrast for standard black-and-white photos.
When shooting portraiture, they reduce lighter skin tones to a pleasing alabaster, though they can wash out some of the red from lips. Red filters also reduce haze and fog, and they’re useful in architecture photography for enhancing the look of brick.
B+W’s #25 Light Red (090) filter is a go-to choice for architectural photography. It makes white facades glow brightly while darkening blue skies dramatically for impressive cloud contrast. Estimated Street Price: Begins at $24.
B+W’s #29 Dark Red (091), meanwhile, darkens deep reds starting in the orange-red region of the color spectrum. The effects are dramatic with extreme tonal separation. Estimated Street Price: Begins at $19.
Good for black-and-white portraiture, orange filters reduce skin imperfections and hide blemishes while emphasizing luminous skin tones, as do red and deeper yellow filters. They enhance texture through increased contrast between blues/greens or reds/oranges, making them a better choice for natural contrast enhancements over much stronger, more emphatic red filters. They darken skies, while reducing haze and fog.