Ever looked at a breathtaking black & white photo and wondered, 'how'd they do that'? The talented photographer with darkroom experience can enhance his/her pictures in the darkroom, but this takes a lot of practice and skill to perfect. In walks the use of filters. Filters come in a variety of colors, each with it's own distinct function.
In black & white photography, there is just one basic rule you need to understand when using filters. Filters lighten their own colors and darkens opposite colors. As you become more experience you will get into knowing when to increase and decrease exposure to get your desired effect.
Filters are used to increase tonal separation of pictures especially in press reproductions. For example the picture of an orange against a blue background would appear similar in black & white creating no tonal separation. In order to correct this use a yellow filter, this will result in the orange being lighten and the background darkened. Yellow filters create a natural look for blue sky's, sunsets, water, green foliage, outdoor portraits with blue sky backdrops. If you want a darker effect in these photos switch to an orange filter. By doing so, your sky and water pictures will be darkened. There will be an increased contrast in your sunset photos and when photographing distant landscapes it decrease haze .
Photographing portraits in black & white can be enhanced greatly with the use of filters. If the appearance of skin is spotty you can improve the tone of the spots with an orange filter. For a smoother tone use a red filter, the use of a red filter also darkens the background making the subject more pronounced. A 29 red filter is the most dramatic filter for use with black & white film. If taking a picture of a blue sky it filters out the blue making the sky look almost black, yet it leaves the clouds fluffy white.
Other colored filters are green - produces very light foliage. Dark blue intensifies haze & fog giving your black & white photo a soft eerie look, it also lightens blue objects for details.
There are polarizing filters. These filters serve the purpose of controlling reflections and in black & white becomes a neutral density filter. Neutral density filters are used to darken an image by letting in less light. For example if your camera is loaded with a fast film for inside shooting and you happen on a can't miss shot outside in bright sun pop on a neutral density filter to darken photo.
The use of filters can dramatically improve your black & white photos or they can project the opposite a more subdued shot. Again the outcome is the personal preference of the photographer.