A few weeks ago I wrote about the UV filter. Several people have asked me to talk about other filters. This blog post is for you.
A photography filter is an attachment that will allow certain kinds of light to be able to pass through. Additionally, a filter is able to reduce or block out other unwanted light sources. In short, the term filter really means anything that modifies the incoming light in some way and includes: polarizing, multi-image prisms, close-up attachments, soft focus, neutral density (ND), graduated ND, and color filters for black and white photography. Filters come in two main shapes: round and square.
Filters add color and a certain touch to a photo that complements the individuals style of photo taking. When you are shooting in black and white mode or film with lens filters, you can darken or lighten the tone of the subjects color. The color filters that are used can darken the tone of an opposite color and brighten the tone of the color filter that is being used. For an example, a red filter will make the red leafs on an autumn tree look very rich and bright, while on the other hand the sky behind it that was blue, is now almost black.
Neutral density filters reduce the light entering your camera so that a slower shutter speed or a larger aperture can be used. Graduated ND filters are used to balance out bright skies against darker foreground scenes.
Another cool filter is called the star filter. This type of filter in photography is placed on the cameras lenses to create a star look effect form any source of light. This is very popular with television game shows and used for portraits to provide a soft overall diffusion. It is also handy with night photography. A split field filter is really a full filter but only half of it is close-up, it is great for taking a picture of something close-up at the bottom like a small flower or bug in focus. The top of the filter has no glass and the camera uses the filter to get the background in focus, say the mountain in the distance.
One of my favorite features about digital photography is the fact that I have the ability to use filters while shooting or the ability to use filters in post-production in programs such as iPhoto, Photoshop, Lightroom or GIMP. The ability to add filters to your images in the post-production phase gives you an infinite amount of options and at times is lighter on the wallet.