Filters for Better Image Quality
There are five basic reasons for using filters: (1) to obtain “correct” color rendition on color film or correct gray tones on black-and-white film; (2) to enhance color images or change gray tones in black and white; (3) to create special effects and moods; (4) to reduce the amount of light reaching the film; and (5) to protect the lens.
Filters absorb light. With light-colored filters (ultraviolet [UV], haze, and some light-balance and color-compensating types), the light loss is so small that it need not be considered in exposure determination. Darker filters, on the other hand, take away a sufficient amount of light to affect exposure. As a result, you need to adjust lens settings ...