Everything you ever needed to know about circular polarising filters

I remember when I first started out in photography I found all the different types of filters to be a bit confusing. I honestly didn’t know my ND Grad filter from my UV filter. And I had no idea about when and why you might want to use a polarising filter. Of course, since then, I’ve studied and learnt a lot.

These days the post-processing options are so good that there are really only a couple of filters that are truly indispensable. One of these is the circular polarising filter. In this video, Christopher Frost walks you through exactly when, why and how to use one.

So what does a polarising filter do? Fundamentally, as Christopher explains in the video, they absorb polarised light, which is normally light that is reflected off a non-metallic surface, including the sky.

In real terms then, what does this do to your photography? Essentially they can reduce reflections from many types of surfaces like water or glass. They also appear to saturate colours more, so foliage will appear greener and skies appear bluer.

Christopher includes lots of examples of with and without the filter in the video, which is a really great way to easily illustrate its effects. He reminds us that the full effects won’t be even on an extreme wide-angle lens such as a 14mm, however, because the filter works best when standing at a 90-degree angle to the sun.

One thing I learnt from this video was that the filter can render screens completely black because often they are emitting polarised light. This makes perfect sense actually since my polaroid sunglasses also create this effect. The other thing to remember is that you don’t have to spend a small fortune to get a good circular polarising filter.