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Why you need to use a polarising filter

Why you need to use a polarising filter

Go Photo CPL Filter

Polarising filters are one of the most important and fundamental pieces of equipment in every serious landscape photographer’s bag. Whether you’re shooting a sunrise, a sunset, or even in the middle of a foggy rain forest, polarising filters are an invaluable tool to help you take better landscape photographs.

There are two main types of polarising filters that you can buy: linear and circular. Both these types of polarising filters have exactly the same effect photographically, however the in-camera metering and auto-focus sensors in most DSLR cameras will not work properly with linear polarisers. This is because the prism inside your DSLR camera that splits off the light for focusing and metering are polarisation-dependent. For this reason,we will only discussing circular polarisers

Circular polariser filters are dark and opaque; and like your favourite pair of polarised sunglasses, CPL filters are designed to reduce the glare from reflected light by stopping polarised light waves. CPL filters are typically round and threaded, screwing into the front threads on your lens, but they can also be square sheets and fit within special holders attached to the front of the lens.

polarising filter

Light that is reflected directly off of surface of an object such as a cars windscreen, water, or leaves becomes polarised. This polarised light is typically seen by us as unwanted glare. By using a CPL filter we can selectively reduce the polarised light and thus reduce the glare. CPL filters are designed to be rotated, and by rotating a CPL filter, the photographer is able to adjust the angle at which the polarised light is reduced. This is especially useful if you want to cut-down the glare from a pond or river, or from the leaves of trees while shooting within a forest. The CPL filter will allow you to bring out more contrast and detail from the scene by reducing the glare from the reflected light.

Rollover the image below to see an example of how using a CPL filter on this waterfall scene has helped to improve the image.

Gheerulla Falls with without CPL Filter

Both of these images are completely unmodified and straight from the camera. They were captured in RAW and converted to .jpg without any modifications or adjustments. You'll notice that the circular polariser filter has helped to reduce the reflected light in the scene. The reflections on the water are reduced, light reflected from the leaves of the forest trees has also been reduced, increasing the contrast and improving the colour saturation. The excessive glare on the wet face of the waterfall has also been substantially reduced, thus revealing much more details of the rocky surface as well as improving the contrast and colour. Incidentally, this lovely location is one of the locations for our full-day photography workshops!

A CPL filter is also great for creating a dramatic, deep-blue sky. Rotate the filter and you can see the difference that it makes. The sky will turn a deep, rich blue as the filter is rotated and polarised light from the particles in the sky is blocked. This can create a dynamic image with lots of contrast and clouds that really stand out.

Using a CPL filter also helps to reduce atmospheric haze within an image, rendering images that are cleaner and crisper then they otherwise would have been without the use of the filter. Haze in the atmosphere caused light to become scattered and polarised, the CPL filter will help to reduce this polarised light and thus return more contrast and colours to the scene.

Unlike other filters such as graduated neutral density and solid-colour filters, the effects given by the use of a CPL filter can not be completely replicated in post production software. Some programs (such as Colour Effect Pro by NIK Software) attempt to mimic the effects of a polarising filter, and while the results can be an improvement over the original image, there's no real substitute for getting it right in the camera.

If you enjoy landscape photography, and want to lean more about the selection and use of filters, then why not come along on one of our intermediate workshops such as the Seascape, Sunrise and Waterfalls Workshop. On this photographic workshop we discuss the different types of filter that are available, how to use them correctly, and how they can help to improve your photographs. You'll also have a fun and hassle-free day out shooting in some amazing locations!

Here's the same image as above, shot with a CPL filter and processed in Adobe Lightroom.

Ryan O'Donoghue Gheerula Falls