A masterclass on polarizing lens filters (otherwise known as a CPL filter) and how they can help take your photography to the next level.
Words and Photography by Urth HQ
Before we get onto the ways in which you could use a CPL filter and the situations best suited to it, let’s run through a couple of the basics first.
A CPL filter – which stands for circular polarizer/linear – is a glass attachment that can reduce the glare from reflected surfaces. Although there are various types available on the market, the most popular is the circular model, partly as it can fit easily onto the end of virtually any camera lens.
When to Use a CPL Filter
There are numerous scenarios we could go through here, so for the sake of space and time let’s narrow them down to a key handful that you’re likely to encounter during your day-to-day snapping.
REMOVING GLASS REFLECTIONS
One of the first things people notice when starting out in photography is how difficult it can be to take photos through a window. A polarized filter grants you the benefits of the polarization effect, which has the ability to reduce all those unwanted light streaks that blur the subject of your shot. It can also do the same for light reflected on water surfaces.
Photographers also find a circular polarizing lens filter handy if they take photos through a window, or of glass buildings, as distracting light streaks and glare that infiltrate a shot can be eliminated. Photos of painted surfaces, such as vehicles or buildings, also create shine and reflections and can benefit from the use of a CPL filter.
A CPL filter will also reduce glare from reflected surfaces, creating clearer images. However, if you take photos of rainbows – which are caused by glare when the sun’s rays and moisture combine – turning the filter to increase the level of glare can actually enhance the rainbow’s color and clarity.
REDUCING WATER REFLECTIONS
One of the most common uses of a circular polarizing lens filter is to reduce reflections from non-metallic surfaces. Any outdoors photographer will be only too familiar with the irritation of reflections, particularly when it’s very bright or sunny. These reflections can easily distract from a photo’s subject. Sticking a CPL filter on your camera lens helps to kick bothersome reflections into touch.
In particular, if you take photos of water or wet surfaces, the filter reduces scattered light and cuts out reflections of the sky or other objects on the water’s surface. This allows the detail of the water, including the surface below it, to stand out.
If you take photos where aerial or atmospheric haze affects an image’s clarity, a circular polarizing lens filter can correct this and add contrast. Photographers who snap shots of distant scenes, such as mountain ranges or cityscapes, argue that a CPL filter reduces atmospheric haze in ways similar to UV filters. This can result in making faraway objects appear sharper with increased clarity and color saturation.
DARKENING THE SKY
Nothing helps give your landscape shot a more foreboding sense of tension than a darker, more menacing-looking sky. The same could be said of shots inside where you’re aiming to create a sinister atmosphere. A good CPL filter will enable you to do just this without making the scenario look unnatural.
BOOSTING BLUE SKIES
This example blurs the line between when and when not to use a polarized filter, as you could justifiably want to increase or decrease the amount of color depending on what you’re trying to achieve. In this case, if you’re trying to boost color in a blue sky then the CPL would come in handy.
Since CPL filters block out certain wavelengths of light you can manipulate the color effect of your photos to add more contrast. If you take photos of the sky, for instance, the filter can add a deeper tone to the blue, or make dull clouds appear more visually striking.
ENHANCING VIBRANT FOLIAGE
For photos of foliage or forests, the CPL filter can add saturation, vividness and contrast. It can transform nature into a richer and more verdant shade of colors. The filter can really come into its own during autumn, when nature’s hues are at its finest. A CPL filter can also banish reflections and shine from leaves, trees or plants, creating clear scenes free from distractions.
ACHIEVING RICHER COLOR
You can also use a circular polarizing lens filter to create darker, richer or more intense tones. This is especially relevant if you want to add drama, atmosphere or even a sense of tension to an image.
Experiment by rotating the filter to create the desired effect, balancing a natural feel with a surrealist look. To achieve the maximum linear polarization effect, shoot at an angle of 90 degrees from the sun or source of light.
When NOT to Use a CPL Filter
Many landscape or outdoor photographers would be lost without a circular polarizing lens (CPL) filter. By rotating a circular polarizing filter, you can block out certain wavelengths of light. This lets you reduce glare, haze and reflections from objects such as water, glass or vehicles. It’s also great for darkening the sky to add a bit of drama to your shots.
Although circular polarizing filters have many great uses, there are some occasions when they do more harm than good. In such cases, they should be left off your lens.
Reflected light can sometimes enhance a photo, especially if the light itself takes on a color other than the usual. For instance, if the sky is red in the evening, this can create a vibrant effect that would be best off kept.
We tend to think of reflected light as negative in photography, attempting to eliminate it as much as possible with a circular polarizing filter. But there are some instances where reflected light can actually add drama and visual appeal to a photo, such as a brightly colored sunset, in which case it would be best not to use a CPL filter.
In particular, if the reflected color takes on a different or unusual hue, this can make an image interesting and unique. Polarized light isn’t always necessarily a bad thing!
THE WET LOOK
Water is transparent and, as such, not always easy to capture through a lens. It can be difficult to tell the difference between a wet rock and a dry one, but allowing light to shine off the droplets can overcome this issue.
If you want to highlight water on an image, this isn’t always easy to achieve through photography, as water is transparent. You can’t always tell the difference between a wet or a dry rock in a photo but by removing your CPL filter, you can capture light shining off droplets of water creating a wet, shimmery look.
REFLECTIONS ON WATER
Reflections on water are the bane of a landscape photographer’s life, but, occasionally, you might think they look pretty cool. If you want to keep the reflections but lose the nuisance glare while ensuring color saturation is boosted, you can still enjoy the best of both worlds.
You’ll need to take two shots, one with a polarizer and the other without. With the help of some post-production trickery, you can blend the two exposures, taking the best bits from each photo. You can also experiment with blending multiple long exposures to see some fantastic results!
ADDING DEPTH THROUGH REFLECTIONS
Sometimes you might want to introduce reflections or shadows to give a sense of depth to an object. Taking a photo of a colored ball might make it look like a flat disk. Adding a slight reflection off the curved surface gives it a realistic, three-dimensional effect. In this case, don’t use a circular polarizing filter.
CPL filters also tend to work best during daylight, particularly on bright days. So you’re unlikely to benefit from this filter if you take photos at night.
When shooting at night you’ll likely want to reflect as much light as possible as there will be very little illuminating your subject in the first place. Any filter that blocks out light in this case would do more damage than good, as explained in our guide to compensating exposure when using filters.
A CPL filter will only serve to reduce light to your lens when shooting at night, which is the last thing you’ll want as you’re likely using a slow shutter speed given it’s already pitch black. Leave your CPL filter off your lens in this scenario. Similarly, it’s not worth using a circular polarizing filter in very low light or completely shady areas, as glare or reflections won’t be an issue.
Another scenario dictating when not to use a circular polarizing filter is if you shoot rainbows. A rainbow is actually just reflected light, so if you stick a polarizer on your lens, the rainbow will vanish. Simply take your CPL filter off, and it will reappear.
CIRCULAR POLARIZING FILTERS ON WIDE-ANGLE LENSES
It’s generally not a good idea to use a circular polarizing filter with a wide-angle lens. This is because CPL filters work best when they’re at a 90-degree angle away from a light source, such as the sun, and a wide-angle lens usually covers more than 90 degrees. This results in an uneven polarizing effect in your photo.
However, if you use a wide angle lens, you might not get an even color throughout the sky with a circular polarizing lens filter. Therefore, stick to a lens no wider than around 24mm. Having said that, you might actually like the effect it creates, so it’s all a matter of personal opinion.
Circular Polarizing Lens Filter versus Digital Post-Production
Although post-production software can alter a photo’s color, it can’t produce the same effects as a circular polarizing lens filter. For instance, reflections and haze can’t be easily removed during post-processing.
If you’re a landscape photographer eager to capture great photos, you’ll struggle without a CPL filter in your kit bag. In fact, when you use a circular polarizing lens filter, you are effectively editing your images in real-time. This saves precious time by not needing to use post-editing software later on.
Do I Need a CPL Filter?
CPL filters have many benefits with no real drawbacks, and form an essential part of every landscape and outdoor photographer’s toolkit. Their ease of use, flexible applications and simple mechanics make for a low-risk, high-reward investment towards creating stronger, more captivating imagery.
They allow you to cut light and reflections, enhance clarity and color, and create images that border on the surreal. They can give your photos more depth, drama and intensity without requiring any additional effort on your part.
Whilst UV filters probably make for the best protective filter, the many benefits of CPL filters make for a compelling reason to add them as a fixture in your kit bag. They may not be a filter to keep on your lens permanently, but there’s no reason to leave home without one!
Did you know Urth makes CPL filters that help stem deforestation? Five trees are planted in deforested areas for every filter purchased. Shop our range of CPL filters here.