Filters are pieces of glass or plastics inserted in the light path to alter the picture recorded. The filter most often used is the UV Filter. These reduced the amount of ultraviolet light reaching the sensor. Back in the film days, this was important since UV light affects some film. UV light has no impact on Digital camera sensors. UV filters protect the front element of the lens.
Each filters inserted in the light path will affect the light and will deteriorate the resulting image. Depending on the quality, the deterioration could be minimal. On most lenses, it is cheaper to replace the front element of the lens than buying a very high quality filter. On most lenses, a small imperfection on the front element of the lens is not visible and will not alter the image quality recorded. Filters on the other hand will cause reflection that will negatively impact the image recorded.
Filters that are worth considering are:
The polarizer help cut haze and reflections and makes for better colors. By rotating the front of it you can increase or cut the effect of polarizing. Make sure to buy a Circular Polarizer on Digital Camera. Linear polarizer could mess with your focusing system.
Neutral Density help reduce the shutter speed. A good one will not alter the light. It will only cut the light. The picture in this article used a neutral density, allowing for a slower shutter speed. This renders the flowing water silkier.
Gradual Neutral Density;
Gradual Neutral Density are usually rectangular in form and need a filter holder in front of the lens. Using these, dim the light that is often too bright in the sky compared with the landscape or subject. These filters stay in position in the filter holder. Positioning them precisely in the filter holder according to the needs of the scene help achieve a better exposure of the scene.
When buying a filter makes sure you buy a filter with these characteristics:
- From a reputable company like Tiffen, B&W and Hoya;
- Look for Multi-Coated or MRC in the properties. This help reduces flares and unwanted reflections;
- On wide-angle lenses, look for Slim Profile. Wide Angle lens usually suffer from Vignette. Adding a filter will increase this negative effect;
- Buy filter for your biggest lens. Step down ring to use the filter with smaller lenses are affordable.
As a rule of thumb, you should pay from 1 to 3 times the number of millimeter of the filter. Good MRC/Slim Circular polarizer of 77 mm are between 154$ and 210$.
Good Neutral Density of 77mm are between 77$ and 154$.
Finally, the best protection for your lens AND your pictures is your lens shade. Putting your lens shade on will prevent side light to reduce the quality of your image, will protect the front element of the lens and will not interfere with the light path.