hi Dan, One of the problems in B/W photography is that ultraviolet rays, the silver halides in the film react very strongly to this wavelength and as such becomes dense on the neg. The atmosphere disaptes this wavelength so that it dosn't form an image but rather a "haze" and the filters that correct them are called haze, uv, 0 or L-39. They do not interfer with other wavelengths and as such can be left on all the time when you using no other filter (it protects the lens)
Remove it if you are using another filter as two filters may cause vignetting. In colour photography UV filters which have a pinkish tint are used to correct an image which would otherwise come out too blueish (overcast days) These are called skylight/correction filters (1A/B or 81A to F resp.) As too which one do you use - there is a breakdown of all the different types of filters on www.filterhouse.com and on www.tiffen.com web sites. I have nothing to do with these companies and only give it as reference though I think you can use skylight filters in B/W but am not 100% sure as I don't shoot B/W. Polarisers are used to increase the intensity of blue skys or reduce reflections or glare on water. It filters out light that has been polarised. Dosn't work on shiny metal though. All filters increase the f-stop by at least 1 except UV's, they usually have the "filter factor" written on them so you know how much to compensate Hope that wasn' too much Feroze
