Why use a CPL or polarising filter and what is a polarising filter?

Have you ever asked yourself what is a polarising filter or struggle to know why or when to use polarising filters?

Before we get to what a polarising filter is and what it does I should also add they are also called a CPL filter and this stands for a circular polarising filter. To keep it as basic as possibly your CPL filter screws on to your lens or fits onto you filter holder, either way the polarising filter can can be turned to increase the polarisers effect in an image or decrease it simply buy turning it.

How do you know when to use polarising filters and why the heck would you use one?

Let’s skip all the technical mumbo jumbo and just talk about what a CPL or polarising filter will do for you.

1. It will help reduce reflections.
2. It will help saturate your skies and forest scenes.
3. It can add about 1 to 2 stops of light reduction.

Reflections

A CPL filter will help kill off reflections in an image, this can provide us with several awesome effects.

Let’s say you are at a lake and there is this gorgeous branch in the water that slowly slips below the water-line and leads you towards your subject for this example a snow-capped mountain (if we are going to pick an example why not make it epic). You are standing there and you can see this with your naked eye but when you take the shot the camera just captures the reflection of the sky on the water and you loose that beautiful leading line in your shot or those precious little details below the water-line.

So you pop on your CPL and you twist it to the right polarisation (damn it a technical word slipped in there but don’t worry about it), lets try that again… you turn the cpl so you kill off the reflection and now you can see through the water to all that sumptuous detail below. You can also play with the effect to just get the right amount of transparency sometimes less is more :-). So that’s the first scenario.

The second scenario is you are photographing a car that your friend is putting up for sale and it’s all nicely polished and super shiny. When you take a photograph of it you get all those annoying reflections ruining your shots… now again pop on the CPL filter and turn it till the reflections on the side of the car are more or less gone. When I saw turn it what I mean to do is to look through your view finder and rotate the cpl filter on your lens as you do so you will see the reflections magically vanish, now they won’t all vanish but you can select the ones you want to vanish by rotating the CPL filter.

Scenario three, you are out to meet a friend in a coffee shop and you see them sitting by the window sitting a cup of coffee and suddenly you think wow what a shot that would be as the reflections in the window create sort of a double exposure effect in your image. You can see your friend in the shop sitting having coffee and you also see the reflected street details in the window. What works really well there is if they are staring out into the street as you see them looking off to the distance and in the reflection you see what they are looking at… I know awesome isn’t it.

When you take the photograph though the reflections of the street are probably going to be too powerful and they could ruin the shot, pop on the CPL filter and rotate it slightly so you can get this amazing mix between just the right amount of refection and your subject to create a real work of art. Can you see where I am going with this? This is gone from a casual shot to you now telling a story and isn’t that what photography is truly all about?

A polarising filter is not just something that’s handy, it can be vital at the best of times and we are still only on the first advantage of using a CPL and it’s reflection killing super powers. So if you thought that was good then read on for some more amazing features of a CPL filter.