Know your stuff
Photographic filters and when to use them There are hundreds of different filters but, essentially, they are all used to correct exposures that can’t be done in-camera. The main ones are:
Neutral density filter
This decreases light entering the lens by an exact amount and without changing the hue or colour rendition (colour cast). The filters are rated ND2, ND4, ND8 and ND16 and each drops the light by one stop. So ND2 = 1 stop less, ND4 = 2 stops less and so on. Neutral density filters are mainly used to slow down shutter speeds in order to get a longer exposure, without affecting the aperture setting.
Graduated ND filter
Similar to a neutral density filter but one side is clear while the other is dark, with a gradual darkening from the middle to the darker edge. When the contrast between your scene and the sky is too high, it reduces the sky’s exposure while keeping the rest of the exposure the same.
Circular polarising filter Used to darken skies, manage reflections or suppress glare, this filter is very effective when shooting in harsh midday light (see images above). It’ll give the image translucent water, a deep dark blue sky and good contrast between sky and clouds. You can set the amount of polarisation by rotating the filter – visible through the lens – but don’t overdo it!