Camera Lens Filters
A camera lens filter is a glass or resin cover that fits over the camera's lens to change the way the image will look at the time of exposure, and sometimes in the viewfinder . The type of filter used determines the extent of the changed effect.
Some photographers will use a clear filter on a continuous basis in order to protect their lens , however, the sharpness of an image can be compromised when using a filter.
Attaching a filter
There are several designs in attaching a filter to the camera lens. A screw-on filter attaches to the screw thread on your lens. These filters are available in different sizes so make sure you choose a filter that fits the size of the lens. They are quick to fit and remove and are less risky to use.
A slot-in filter needs to be used with a dedicated filter holder that attaches to your lens via an adapter ring. Make sure the adapter ring and filter holder are the correct size for your camera lens.
Types of filter
Protective filters are clear, don't affect light exposure and can be used all the time to protect the camera's lens from dust, dirt, moisture and scratches. Alternatively a ultraviolet (UV) or skylight filter can be used as a protector. They allow light to pass through the filter, but will avoid excessive ultraviolet light and haze from penetrating, leading to improved contrast and colour of images.
A polariser filter reduces and sometimes removes glare and reflections from reflective surfaces, can make a blue sky darker and increase the colour and saturation of an image. Available in linear and circular types, a photographer can adjust the degree of glare that is reflected as it absorbs the light. However, linear filters can affect the metering and AF systems on later model DSLR cameras.
Neural density (ND) filters reduce the amount of light that enters the lens and are used when a large aperture or slow shutter speed is required. They are available in different strengths. Graduated ND filters are half clear and half tinted. They filter only part of the image and are for use in slot-in filters.
Black and white filter sets are comprised of four coloured filters. The red, orange, green and yellow filters provide a variety of effects that change the colour and hue of an image and enhance certain features. White balance filters are used to ensure better colour accuracy and are available in different sizes. Close-up filters, also known as macro filters, improve image clarity when taking close-up photographs.