Why use filters in photography anyway?
Have you ever been frustrated by a scene full of contrasts where a bright sky overpowers a darker foreground?
Have you ever wanted to reduce reflections in water scenes and enhance the colours of the surrounding scenery?
Have you ever wished you could recreate the beautiful silky flowing water or streaky cloud movement that look amazing in other photographer's images?
If you answered yes to any of these questions, then that's exactly why you NEED filters!
Using a Circular Polariser to enhance colours and reduce reflections
A circular polariser has a multitude of uses - it can enhance the blues in the sky on a sunny day or it can reduce reflections on water and wet rocks and really bring alive the lush colours of the scene before you.Here's two side-by-side images - no CPL on the left and using a CPL on the right. You can see how the reflections are greatly reduced in the image on the right.
In the next example you can see how much the sky is enhanced on a blue sky day by using the circular polariser - it also brings out the golden hues of the grassy landscape as well.
Using a Graduated Neutral Density Filter to create balanced exposures
This is my MOST used filter - I'm never without it especially at sunrise and sunset when the contrast between sky and foreground is most extreme. The filter evens out the exposure between the two, darkening the sky so that you get a much more balanced exposure across your image - it makes editing your images so much easier when the exposure, highlights and shadows are more even so it gives you a great base from which to edit the image to make global adjustments.
Using a ND filter (6-stop or 10-stop) for long exposures
Long exposures can transform an ordinary scene to something quite magical. And the strength of which ND filter you'll want to use depends entirely on the available light in the scene. Personally I use my 6-stop (ND64) a lot more than my 10-stop, so if I had to pick just one to purchase that would be it!
A long exposure can create an amazing silken water effect in river, waterfall and beach shots. The example below is a 15 second exposure of a small stream in the Waikato near Pirongia.
On a windy evening with passing cloud, this 30 second exposure captured the streaky sight of cloud movement overhead which introduced a very cool effect into the scene.
At the beach, a 30 second exposure can smooth out the waves creating a silken smooth effect to the waves and the clouds above.
At Lake Wanaka, a 56 second exposure creates both lovely cloud movement and smooths out all the ripples (AND DUCK MOVEMENT!) on the lake.
So what filters should you buy?
Not all filters are created equal. There are some very cheap filters out there in the market and generally you pay the price in terms of quality. There's no point having a really nice camera body and quality lens capable of taking amazing images if you then go and put a really cheap piece of glass in front of it - not only will you lose sharpness but you're likely to lose the true colours of the image you're trying to capture as well.
Circular vs Square Filters - which is best?
There are pros and cons of both and it really comes down to a balance between your budget and the flexibility you need.
PROS - generally cheaper and can be more robust
CONS - can be less flexible. Using a circular graduated filter is not as good as you'll have a fixed position for where the graduation lies on the horizon and the only way to change it will be to move the camera position rather than adjusting the filter position.
Although you can stack circular filters, you might find you get vignetting due to the rounded corners of the filter against the lens.
PROS - you can switch over the whole filter kit set up between lenses relatively quickly and easily with different rings. You can easily stack a polariser and 2 ND filters together for effect and there should be little or vignetting.
CONS - more expensive as you need to purchase a holder to use them with and they can be more prone to breaking when dropped (although some filter brands like KASE Filters have developed shock resistant glass.
The filters I recommend
I've used several different brands of filters and the brand I recommend most highly are KASE Filters. You can read my review of both their square and circular filters here: KASE Filters - the must have addition to your photography kit.