Christian Photographers Community

Neutral density filters are grey in colour, and simply reduce the amount of light reaching the film usually by about one to two stops, they are used when you want to use longer exposures, say when on a sunny day you want to capture movement in a field of flowers but because of the brightness your shutters speed is too fast, a neutral density filter will let you use a shutter speed of 1/8 second instead of 1/30 second, they don't affect the colours of the picture because they are neutral, i.e. grey.
   Neutral density filters are for film cameras basically because you can't alter the speed of the film, like you can on digital, although they can be used for the same purposes with digital.
   Say you wanted a shot with very shallow depth of field, and the brightness of the light was forcing you to use an aperture of F8, put an ND filter on and you would get an aperture of F4.
   Graduated neutral density filters are perhaps the most useful, as they darken the area of the sky by holding back the light in that area, simply put these filters are half grey at the top, and half clear at the bottom.
ND filters simply reduce light coming through them, that's all, try using the word sunglasses for neutral density filters, that's all they are.

Thank you, Summicron.