Working in Black and White Photography, I always find myself in a bit of a pickle when it comes to using filters. Mainly because I have not used them very often and always because I find their workings confusing. I should learn to remember that as a rule of thumb, a colour filter lightens the reproduction of objects of it own colour but darkens the complimentary colours. YELLOW Changes using the yellow filter are subtle so it's used by many photographers as a lens protector and most benefit is seen in landscape photography where the effect on blue is just enough to make a light sky a shade darker than the print's border. I know I use it when I see a beautiful formation of fluffy clouds, which I know will not have enough contrast on film to print easily! ORANGE The orange lightens reds so it's favoured by portrait photographers who use it to reduce freckles and skin blemishes. Architectural photographers also find it's affect on bricks useful. This out of all the filters is arguably the most practical. RED Red is for the creative photographer who likes contrasty results, as tones are dramatically affected. It's also used by infrared photographers as an alternative to the true infrared filter and very popular with landscape shooters. GREEN Green is less popular in the black & white photographer's kit, but would be appreciated by landscape photographers as it affects greens and can help differentiate between foliage making the whole scene come to life. The downside is it lightens the blue in a sky so the overall contrast may suffer. BLUE Blue is little used for black & white work and would mostly be considered as a contrast reducer which you can often do satisfactorily using a different paper grade.