Gentlemen, since we are starting to talk about filters and the effects they provide our B&W shots, I rummaged through some old Word files and found this handy reference.  I am sharing it here without any idea of its origins.  Apologies to whomever created this originally: 
 
  B+W UV 
Black and white films are also sensitive to the effects of invisible UV light. A high percentage of UV light, present in a clear view at the sea or mountains, results in a hazy and washed out picture. The UV filter blocks out this light. Filter factor is 1.0.  
  
  B+W light yellow 
Accentuates warm, soft, delicate scenes through the enhancement of yellow, orange, and red. It is especially suitable for portraits of women and children, skin tones in natural light, springtime landscapes, and nature scenes. Filter factor is approx. 1.5.  
  
  B+W medium yellow 
Creates subtle differences between green tones and enhances the natural rendition of the sky. Recommended for landscape and foliage photography. It tones down skin blemishes and ruddiness in daylight portraits, and results in soft skin tones as well as intensified blond hair. Filter factor is approx. 2.  
  
  B+W dark yellow 
Distinctly improves reproductions of fine structures such as sand or snow, increases contrast of foliage, and clears distant haze. It diminishes skin blemishes and freckles in artificial light. It also darkens eye colors and lightens lip colors. Filter factor is approx. 3.  
  
  B+W yellow-orange 
Bright-orange filter darkens blue and violet as well as green and yellow-green. It is indispensable for all landscape and architectural photography, which requires vivid and clear contours. The sky is distinctly toned with the clouds clearly contrasted against it. This filter is popular for nude photography under natural light. Filter factor is approx. 4.  
  
  B+W red 
Creates a strong darkening of the sky, dramatic storm-like cloud reproduction, and strongly enhanced shadows due to its enhanced contrast. It also achieves good tonal differentiations in still-life photography by brightening yellow, orange, and red. Filter factor is approx. 4.0.   
  
  B+W yellow-green 
Ideal for scenes where it is important to differentiate the green tonal values. The application is especially suited to landscape photography in the springtime because it enhances the light green color of the leaves. Due to its favorable effect on red tones, this filter is also suitable for portraits or group pictures taken in natural light. Filter factor is approx. 2.  
  
  B+W green 
Dark green filter creates distinct differentiations of green tones in late spring and summer. Also recommended for floral pictures that are used graphically, for tonal separations in still-life photography, and for the correction of red tones in portraits with high-speed film. Filter factor is approx. 3.0.  
  
  B+W light blue 
Recommended forthe correction of artificial light with overtones of yellow-red such as with older photo lamps or normal household bulb illumination. Also used to darken skin tones for portrait or nude photography under natural light. Filter factor is approx. 1.5.  
  
  B+W blue 
Blue enhances the tonal rendition of the sky by emphasizing mist in valleys and transmitting light rays over water, fog, and haze. In addition, this filter is used for the tonal separation in still-life photography and the correction of the light spectrum from artificial light sources. Filter factor is approx. 2.  
  
  B+W light red 
Ideal for enhancing contrast in landscape and architectural photography, and it enhances white areas.  For example, letting clouds stand out clearly against a darkened sky and drastically reducing distant haze. Also used for tonal separation in still-life photography. Filter factor is approx. 5.  
  
  B+W dark red 
This filter gives a surrealistic effect in landscape and architectural photography by producing a "storm-like" cloud effect, "moonlight" effect, and "wood" effect. It is indispensable for tonal separation in still-life photography and for the reproduction of documents, which have become illegible. Filter factor is approx. 8. 
 
Hope you find this useful. 
 
Dave Chevalier 

Ogden, UT