While there are dozens of different types of filters you can put on your lenses for different effects, there are three very common filters that everyone should have in their camera kit, the circular polarising filter, the neutral density filter, and the UV filter. In this article we will discuss what these three filters are and the effects that it can add to your images.
When we are talking about these filters, we are talking about glass filters that screw onto the end of your camera lens. For you point and shoot camera people, this unfortunately does not apply to you, these filters are only available for SLR type cameras.
Circular Polarising Filter
The Circular Polarising (CP) filter is just like getting a pair of polarised sunglasses, it will knock out a lot of glare and reflections as well as bring out the colour by blocking certain wavelengths of light. With a CP filter, you can adjust from no filtering to full filtering by rotating the outside ring of the filter depending on how much of an effect you want.
This will cut down the amount of light entering the camera so you may have to adjust your aperture or exposure to compensate. To demonstrate the effect, we took a series of photographs of a fountain at a local park. The following two images show an unfiltered image and the second is with the CP filter on.
Note how the water and sky are bluer and the trees are greener, this is because atmospheric haze and reflected sunlight are reduced and overall colour saturation is increased. Polarisers are often used to deal with situations involving reflections, such as those involving water or glass, including pictures taken through glass windows. When shooting outdoors, you should always have a CP filter on and adjust as needed for the best effect.
Neutral Density Filter
Another of the common lens filters is the Neutral Density filter (ND) is simply a light blocker. If an image is too bright and you can’t compensate with a faster shutter speed, then an ND filter can be used to get the light back under control. Another common use of an ND filter is to blur motion in a scene that would otherwise end up being overexposed on a long shutter speed.
Take this fountain shot for example, this was taken at noon with no clouds, anything however the fastest shutter speed and the fountain would just be a glaring white blob from being overexposed, the problem is that this is not a very pleasing picture of the fountain, I would prefer a longer shutter speed to give the water a silky appearance. An ND filter is exactly what this is for. Here is the unfiltered shot and the same shot with an ND filter.
You can see that this is a nice improvement over the unfiltered image, however it is actually lacking in colour because the light was so harsh. So what can you do? Well, to start, there are different grades of ND filters from light to heavy to cover different situations. You can also stack filters and use multiple filters at the same time. The following image combines both the ND filter and the CP filter.
Because both the ND filter and the CP filter both block some amount of light, we were able to use an even longer shutter speed creating a very nice image of the fountain and getting the advantage of the CP filter for bringing out the colour of the sky and the trees.
A third filter you may want if you are doing landscape photos is a graduated ND filter. This filter is darker on the top and clear on the bottom. This filter is used to block of some of the light on the sky allowing you to use a different exposure or longer shutter speed to get the exposure on the landscape correct without blowing out the sky from it being too bright.
While the UV filter, another common lens filters, is supposed to cut down on UV light and help with haze, I can never tell the difference when I use it or not. Then why would you want one? This is a simple answer, these filters are the cheapest filters available and since they basically make no difference, you should ALWAYS have a UV filter on your lens, this will help protect the lens from damage. I would also rather be wiping off dust and fingerprints from a UV filter rather than my more expensive lens glass.
Now get out and start shooting!