Photography News Issue 37

Photography News | Issue 37 | absolutephoto.com

Technique 38

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Polarising filters

Without polariser

©KingsleySingleton

GearGuide: Cokin P164 Circular Polariser Filter £69.99

With polariser

©KingsleySingleton

To control reflections and achieve effects like those here, you can use a Cokin P164 Circular

It physically changes the look of a picture in ways that software can’t

Polariser filter, which slots into the regular Cokin P-series holder. The P164 occupies the first of the three slots, so that other filters can be used in front. When in the holder the polariser can be rotated via slots in the holder, allowing you to reach its notched edges. The P164 is available to fit Small (A-series), Medium (P-series), Large (Z-Pro) and Extra Large (X-Pro) filter holders.

Top One of the benefits of using a polariser is control over reflections in the scene. You can choose to shoot with or without them. Bottom Because polarisers reduce glare they can also make colours more intense.

With polariser

©WillCheung

What they are: Like full ND filters (and to an extent Graduated NDs, too), the effect of a Polarising filter cannot be replicated in post- processing; it physically changes the look of a picture in ways that software can’t. Polarising filters work by blocking light that’s reflected from the subject along certain angles, and this loss of this light reduces glare, controls reflections and, via the more diffused light created, enlivens colours and contrast. The ‘circular’ part of Cokin’s P164 Circular Polarising filter comes from the construction of the filter, not its shape, and is in reference to the fact that it can be used with a digital camera’s metering and AF systems, whereas ‘linear’ polarisers cannot. Polarisers come in screw-in and slot-in types. When to use them: Most landscape situations can benefit from the use of a polarising filter, but its effect is limited by the direction you’re composing in relation to the angle of the sun. Overcast days won’t show the effect as much. Different surfaces and angles in the scene can also cause different results: in some situations, like shooting wet rocks, a polariser can reduce glare and lower contrast, while in others, such as with white clouds in a blue sky, contrast can be noticeably increased. When shooting water (and glass), a polariser can also remove surface reflections, allowing submerged subjects to be more visible. How to use them: First you need to find an angle in relation to the sun, that the polariser

will work but it’s worth remembering that this shouldn’t be allowed to dominate your composition. The optimum effect will always be at right angles (perpendicular or 90°) to the sun. To gauge this, you can point at the sun and raise your thumb, so it’s perpendicular to your index finder; rotate your hand, keeping the finger pointed at the sun and your thumb will point to where the filter has most effect. Next you need to rotate the filter itself, which determines which angles of light are filtered, so look through the viewfinder to do it. And because a polariser is blocking light you’ll notice that there’s a fall in the shutter speed as its effect increases. At maximum this should be around two stops, but can be more. Anything else? Yes, and it’s of particular concern for landscapers. Because the amount of polarisation is relative to the position of the sun in the scene, wide-angle views can show the effect in a patchy way. So, while the filter works strongly in one place it will fade away from the point of maximum effect. This also applies if you’re shooting panoramic images, where the effect will increase and decrease as you turn through the frames. The solution is to rotate the filter to lessen the effect, which can stop pictures looking unnatural anyway. Or you can use a longer focal length to hide the fall-off through cropping. You can also frame so that the polarisation increases from one side of the image to the other, much like a GND would.

Without polariser