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

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 one?

What a polarising filter? A polarising filter or CPL as they are also called is a usually a round filter that screws onto the front of your lens or fits in your filter holder.

Which bring us to what does it do and how do use it…

A CPL will…

  1. Help reduce reflections.
  2. Help saturate your skies and forest scenes.
  3. Add about 1 to 2 stops of light reduction.


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

Water and Lake photography

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 let’s say 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 when you move around but when you take the shot the camera just captures the reflection 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 beautiful 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.

Cars and Shiny objects

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 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 on your lens as you do, you will see a lot of the reflections magically vanish, now they won’t all vanish but you can select the ones you want to kill off by rotating the filter.

Street Photography uses

Scenario three, you are out to meet a friend in a coffee shop and you see them sitting by the window sipping a cup of coffee and suddenly you think wow what a shot that would be… The reflections in the window create a sort of a double exposure effect in your short. So, you can see your friend sitting having the coffee and you can also see the reflected street details in the window. What works really well here is if they are staring out into the street it’s like they are bringing the image to life as you see what they see even though you are looking the wrong way, nuts 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 your CPL 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 has gone from a casual shot to you now telling a compelling 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.


A CPL will add pop to your skies and enhance the blues and overall saturation of your image. If you’re shooting a forrest scene they work wonders, really helping the colours come to life which in turn makes your image pop. So as a saturation booster they really help, as an added bonus they will also darken the blues in the sky a bit to help you balance your overall exposure.

For the last one you will have to stick with me for a bit as I explain why light loss in a CPL is sooo handy.

Light reduction

If you have been following my blog posts you will know I love the Elia Locardi filter kit by Formatt Hitech (review of it here).

It comes with a great combination of filters and the awesome Firecrest 100mm MKii filter holder (review here) which has a CPL included in the kit.

So picture this you are at the beach shooting a sunset and you are currently using your 10 stop ND filter and it’s giving you about 30 seconds of an exposure but now you want to go for let’s say a 1 to 2 second exposure to give you that slight motion blur in the fast moving water scenes like below.

Your next weakest filter in the kit is the 4 stop ND filter. This will give you half a second which is too fast all together but if you pop n the cpl and the 4 stop filter just like magic you are now using a 5 to 6 stop ND filter. Isn’t that a handy little feature to have?

When you pair the ten stop, 4 stop and cpl together you get the below possibilities of ND strengths.

The Firecrest filter holder is able to stack ND filters due to the unique extra light light shields it has.

Total ND        Combined filters

4-stop      =       4-stop ND

5.5-stop   =   4-stop ND and CPL

10-stop     =     10-stop ND

11.5-stop  =  10-stop ND and CPL

14-stop   =   10-stop ND 4-stop ND

15.5-stop = 10-stop ND, 4-stop ND and CPL

Now that is a lot of options from just 2 filters and a cpl. You also get the 3 stop Graduated filter in the kit which helps you balance out your sky and foreground exposures.

That is an incredibly short and sweet break down of why you need to shoot with a CPL or at least have one in your bag and if you are buying an ND filter system make sure you get a cpl in the kit and don’t pay through the nose for it.

Have a look at my photography tips and tricks section in the menu where I cover everything from…

Photography editing Software,

ND Filters explained and how to choose the right ones,

Photography tips everything from filters to tripods,

Seascape Photography explained,

How to backup your photographs,

Golden hour photography tips,

My secret tips to photography,

My Photography Workshops,

My Photography Story

Jpeg vs Raw

I am a brand Ambassador Featured Artist and Photography Educator for Formatt Hitech filters and I am delighted to be able to offer you the following discount code…

Don't forget to use my Formatt Hitech Discount code to save yourself 10% 🙂

I should add for the sake of transparency that every time a product is purchased with my code I get a slight commission for the sale but this helps me write blog posts like this and hey you get 10% discount so it’s win-win for everyone.

See you out there,