We’ve explained the three main types of filters before, now from Beyond Phototips here’s more on filters and what they can do for your photos:
Color Filters** essentially add and subtract color from the scene. For example, a yellow filter allows the frequencies of light that show up as yellow to pass through while reducing light of the opposite color, blue. This is useful to know when you’re using filters for color correction and when using filters for black and white photography. We’ll discuss those in more depth later, right now I want to get to the more interesting, special effects filters.

Starburst Filters are good if the subject that you’re photographing is dark point sources of light. Take a small city road at night, for example, most of the scene is dark with some lit areas and some street lights. The streetlights are point sources of light and when used with this filter will diffract into star patterns.

Diopter Filters are also called close up lenses. They allow you to focus at closer distances, making it ideal for close up or macro photographs. They are cheap compared to macro lenses or extension tubes/bellows and are a great way to explore the world of macro photography without the expenditure.

Soft Focus Filters are filters that slightly diffuse a photograph. Most soft focus filters have a more pronounced effect in the brighter areas of the photograph. As the name suggests, Soft Focus Filters make the photograph look soft. This is useful for portraits where the photographer wants to achieve a nostalgic or ethereal look or maybe just give the photograph a diffused, glowy feel. Some photographers also use an old UV filter smeared with a thin coating of petroleum jelly to get a similar effect. The advantage of using this method is that the photographer can smear the outer edges alone and leave the center sharp.

An important point to note is that cameras with Through The Lens (TTL) metering – which means all modern SLR cameras – will automatically adjust for all filters that are fitted in front of the lens. So, don’t worry about compensating for them. If you have an older camera, which uses manual metering, and uses a lightmeter that does not take readings through the lens, you may have to compensate for each filter’s filter factor.