Polarising Filter - Introduction

Want to boost your colour saturation at a stroke, without going near a computer? Buy a polarising filter.

Polarising filters work by suppressing reflections that occur on most surfaces. In the right conditions reflections on the surfaces of water and glass will vanish, allowing you to see more clearly through them.

But the contrast and colour saturation in your photos dramatically improves too. Blue skies become bluer, clouds stand out more, trees and grass look greener, and all the other colours in your scene seem richer. The transformation happens instantly, before your eyes, and cannot be replicated on a PC. Polarising filters work best on sunny days with the sun at an angle of about 90° to the subject. On grey, overcast days they may have little or no effect.

Types of polarising filter

There are two types of polarising filter: linear and circular. This isn't a reference to the shape of the filter itself - most are round - but to the way in which they polarise the light. For digital cameras you need the (sadly more expensive) circular type.

Make up of polarising filters

Most polarising filters are comprised of two connected rings that rotate independently of each other. Once you've screwed it onto the lens, the front part is rotated until you get the polarising effect you want.You can also get polarisers that slot into filter holders such as those from Cokin and rotate within the holder. Whichever kind you get, they all reduce the light entering the lens by about 1.5 to 2 stops, so you'll have to compensate accordingly.

Choosing a polarising filter

When choosing a polarising filter you'll find a wide disparity of prices, even within the same brand. Hoya, for example, sells a 67mm polariser for under £50, and another for over £100. What you're paying for is superior optical glass, anti-reflective coatings, and perhaps superior engineering in the mount. Some boast a thinner profile so they're less likely to cause vignetting when used with wideangle lenses.

Whether these things are worth the extra cost to you is a personal choice. If you use premium quality zoom or prime lenses (such as Canon's L series optics) it's probably worth investing in the best polarising filters to go with them; otherwise as long as you stick to one of the main brands listed here, you're unlikely to be disappointed.