
Sam Wilson
Give Your Photos Some Extra Pop With This Filter
A Guide To When And How
A Circular Polarising Filter (CPL) can be a photographer’s best friend, but it’s really important to know when and how to use one to its fullest potential.
The aim of the following guide is to explain just how without too much technical jargon.
What Is a CPL?
A circular polarising filter is a filter that you attach to your lens that can greatly enhance your photos if used correctly. It cuts down on certain types of light and can improve overall contrast in a landscape.
There are many articles explaining the technicalities that are not going to be covered here, but think of it as similar to wearing sunglasses to reduce glare as the simplest explanation of what they do.
Everyday use of polarising filters - good old sunnies! (These 2 images are courtesy of Canva)
While there are several brands and styles, this article will focus on the type that screws onto the end of your lens.
What does a CPL do?
Eliminates glare and reduces reflections on water so you can see into the water (see example below). This is also helpful to reduce glare on waterfalls caused by sunlight.
They can also help to reduce reflections on other surfaces such as glass and metal.

Darkening and saturating the sky - particularly helpful when shooting during the day when there is a high contrast due to the harsh light of the sun. They are most effective if you can position the sun off to the side as it will have little effect if the sun is either directly in front or behind you.

Saturates colours - this works particularly well with foliage - think forests and waterfalls

This day at Hopetoun Falls was the day the penny dropped for me with a CPL. Taken back in 2018 I can't show a comparison but I'll compare it to a light bulb going off. I was on a workshop and was shown the technique of zooming in on the camera's LCD screen and 'spinning' said CPL. It totally blew my mind the difference it made. I'd almost go as far to say that I hardly felt the 200 stairs back out - 'almost' being the operative word. Once you have that revelation you can't go back.
Slows down shutter speed as it reduces the amount of light coming into the camera. Depending on the type and brand, this can darken the exposure by 1-3 stops - beneficial if you are looking for a slightly longer exposure during the day or at waterfalls for example

When Not To Use One
As wonderful a tool the Circular Polarising Filter is, it's not something that is to be used at every opportunity. It can in fact 'ruin' your image, and here are some examples when this is the case -
When shooting into the sun - not only can it’s effects be minimal in this case, it can actually enhance ‘flare’
When there isn’t enough light.
As it slows down the shutter speed, this is generally not an issue if shooting on a tripod, but definitely something to consider if you’re shooting hand held. No one wants blurry images.
When you want to keep or enhance a reflection such as at a lake or on a building.

Uneven polarisation can occur –
As said before, they work best when the sun is off to the side, and if the light is coming from directly behind or above, patchiness and ‘blobs’ can occur in the colour of the sky. This can also happen when using an ultra wide lens, so always check before leaving.

Conclusion
I consider this an essential part of gear and one lives in my bag, but always remain mindful of when to use them, and when not to.
They are considered an essential piece of gear by many photographers as this is one effect that cannot be rectified completely in any editing program to date.
I'll finish up with another example of when a Circular Polarising Filter saved the day -

That’s it for now - Keep smiling and stay caffeinated
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