Why You Should Own a Polarising Filter
Filters are perhaps the most discussed photography accessories of all. Key staples of the film era, where pretty much everything had to be done in camera, there used to be a huge range for sale. All from straight forward ones for colour balancing to fun creative ones that added in rainbows or gave the appearance an object was moving at super speed, there was plenty to choose from. Flicking through an old Cokin booklet certainly opened my eyes to how creative you could get using simple filters (and raised a few eyebrows at the numerous images of scantily clad women within, but I guess we should not expect anything less from the French in the 1980’s).
An example of a circular polarising filter (CPL).
Whilst there are some die-hards out there who still swear by their UV filters, in the digital era almost all of these have disappeared due to redundancy. Colour balance can now be changed in camera at the flick of a dial and any creative effects you want can be created more precisely in post-production with the likes of Photoshop. However, there is one type of filter that sits unique amongst all of them, doing something that cannot be replicated in post processing, and therefore the one you really must own – the polarising filter (most typically as a circular polariser (CPL)). Without getting into too much physics - as some portion of light in the sky and from reflections are linearly polarised, by rotating the CPL you can block some of this light to reduce glare & reflections as well as increased contrast and colour saturation. Here is a visual explanation:
Without the polarising effect…
…With the polarising effect. Notice how the reflections in the water have been reduced and the contrast & saturation of the foliage has been increased. The latter is very obvious if you look at the patch of dead leaves in the foreground. Comparing your own images side by side on your computer will make the differences even more obvious then seeing them here.
You cannot replicate this effect entirely in post production as if your camera did not capture the information in the first place due to glare or a reflection then it cannot be edited. Of course, you can alter the strength of the effect by spinning the filter in a different position, sometimes the full effect can give the skies an unnaturally dark look that may not work for a composition. The area of photography I use CPLs the most is car photography. As you can imagine cars are one big shiny object made up of metal and glass and reflect light like crazy. You cannot remove all the polarised light across the frame all at once with a CPL but what you can do take multiple images with the filter at its peak in both positions, and then comp them together in Photoshop to cover the entire car. I will do a blog post explaining this in more detail in the future but here is an example of before and after.
Having the filter spun in one position allows you to reduce and remove reflections from the car windscreen…
…and then switching it around allows you to reduce and remove reflections on the side of the car…
…Finally by combining the two images in Photoshop you can reduce and remove reflections across the entire car and finish making your final adjustments. Shooting two different images also gave me the opportunity to remove unwanted hot spots created by my flash.
I have also found my polarising filters to be useful when shooting video as they act as a weak neutral density filter to allow me to shoot at slower shutter speeds, alongside reducing the bright glow of the sky.
Buying Advice
When it comes to purchasing one you will quickly realise you will need to buy a CPL for every filter thread size you have for each of your lenses. This can get expensive as cheap filters are not worth the money you pay for them; they do not function very well and often show a noticeable drop in image quality. Your best bet is to pick a mid-range option, as they are high quality but not breaking the bank, and while they may not have all the same coatings as the top-of-the-range filters, you will not notice much difference beyond your bank balance. I suggest your first purchase should be a size that either is for your most used lens or covers the greatest range of lenses in your bag. One way you can get around this though is to buy a cheap set of adapter rings that allow you to fit filters of different sizes to your lens. That way you can purchase the biggest filter size you require and then use the adapter rings to be able to use it on a smaller filter thread. If you so choose to only own one then take extra care to look after it, they can get damaged with marks and scratches which can show up in your images if using smaller apertures such as F16.
So, there you have it, some filters are still useful in the digital era and polarisers are at the top of that list. Do you own one? If not, then I hope this blog has inspired you to get your first one. As ever leave you comments down below.
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