What Does a Polarising Filter Do? How to Use it and it’s effect on Photos

The polariser is one of the most used filters in photography as it allows you to eliminate unwanted reflections from your scene. This effect is not possible to reproduce in post-production (well maybe you could, but it would take hours and hours vs the seconds it takes to rotate the pola) and its uses are manyfold in many photographic disciplines. In this article we will discuss how to use it, the effect it applies to our photo and the various types that we produce.

There are two primary types of polariser. Circular Polarisers (often referred to as CPL’s) and Linear Polarisers. “Circular” doesn’t in fact refer to the shape of the filter, it refers to the orientation of the polarised light. So you can have a square circular polariser. Still with us?

Linear polarisers are not compatible with most SLR cameras as the way the linearly polarised light travels and splits can interfere with AF, light metering and anti-aliasing filters. So in photography, the predominant polariser used is a CPL which is in fact a Linear polariser with an additional layer that takes the linearly polarised light and converts it to circularly polarised light. 

By Dave3457 

How to use the polarising filter

The use of the polarising filter is very straightforward, mount it on the front lens, or on the adapter ring if we use a holder like the NiSi V7, and then we rotate the filter itself or through the appropriate wheel on the holder. Both in live view and through the viewfinder we will see the effect on the framed scene change according to the rotation. When we find the effect we like best, we take the shot. If we use the NiSi V7 we can also mount up to 3 square filters, such as ND filters for long exposures, together with GND filters to balance the sky.

Tips for using a polariser

Like any aspect of photography it is important to know your tool and its limits. The polariser can prove to be a double-edged sword if you do not pay attention with wide-angle lenses;  always check that no annoying halos are created due to unequal polarisation, which is normal in every polariser and can be used to your benefit. For example, we can polarise only the sky or only the foreground. Like any accessory that adds a level to our optical system, it is important to aim for maximum quality. Low quality polarisers reach a very low polarisation level and can introduce flare as well as reduce the overall image quality. If we use other filters, especially ND, it is important to take into account the convenience on location of using square filters with a specific holder which is more convenient and practical.

Examples of photos with polariser

Let’s move on to more practical examples that show what the polariser is actually for. We will focus on landscape photography but this is not the only area where the polariser is useful for reducing reflections, enhancing colours and limiting haze (and the often overlooked advantage of removing the sheen from foliage in forest photos.)

In still life, a polariser can be very useful when there are reflective surfaces to photograph, for example a wristwatch or jewellery. Also in portraiture there are situations in which having a polariser at hand can be useful, for example to photograph through a glass, the windshield of a car or simply to be able to control reflections if too intrusive.

Polariser in landscape photography

Landscape photography is most likely the photographic genre where the polariser is most used, so for example…..

Attention: In the two photos above the polariser was added and rotated to polarise the upper central part of the sky. No other type of modification or adjustment has been made and no other filters have been used besides the polariser.

The difference is clear. In this shot the effect of reducing the haze is evident and simply by rotating the filter we have improved contrast and readability in the highlights. From this photo there is also evidence of an often underestimated feature of polarising filters, that is the ability to increase reflections as well as eliminate them. Being a selective polarisation, it acts on the sky and the reflection in the water gains intensity because it reflects a much more contrasted sky. It remains at the discretion of the photographer to polarise the foreground or the sky. NiSi offers different solutions for the photographer who wants to use polarising filters, in the V7 holder kit there is a high quality polarising filter and everything you need to use ND and GND square filters. For a comparison of the 3 NiSi CPLs (PRO, Landscape and True Color), click here.

Differences between Standard PRO polariser and Landscape Polariser

The Landscape CPL and the True Color CPL offers two main advantages compared to the kit with standard PRO polariser:

• Unique polarising film, with declared polarisation of 99.5%!
• External Nano Coating (NC) treatment, water-repellent and oleophobic for simple and precise cleaning

The greater polarisation means that the Landscape filter slightly increases the saturation of the photo, at least in the blue channel*, while True Colour CPL aims to achieve the best possible colour match.

*A completely normal effect due to the very intense polarising film. For this reason, some photographers decide to equip themselves with both types of polarisers.

True Color CPL polariser

The film developed by NiSi for the True Colour CPL aims at maximum polarisation, uniformity and colour fidelity. Classic polarising filters are naturally prone to yellow/green dominance. Thanks to the use of the latest technology, we have developed a polarising filter for those seeking maximum colour fidelity, eliminating any kind of dominance. The True Colour is also available as a kit with the NiSi V7 and the S-Series 150mm Holder.

You can find out more about the differences between CPL PRO (standard), Landscape and True Colour in this article.

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