CPL vs Linear Polarizing Filters

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Can’t decide between a CPL or linear polarizer filter? Check out our expert advice to find out which filter suits your shooting style best.

Words and Photography by Urth HQ

Polarizing filters offer many benefits to photographers, especially those who specialise in outdoor and landscape photography. There are two types of polarizing filters: linear and circular polarizing filters. Each type is used for a particular benefit, read on to discover which might be the best fit for your shooting process and style.

What are the differences between CPL and linear polarizer filters?

Before working out which type of polarizing filter is right for your camera, it’s helpful to understand the principle behind polarizing filters.

Essentially, polarization refers to the way in which light behaves or moves as it hits your lens. Light travels in waves, and when light is reflected off non-metallic surfaces this light is bounced and scattered, which makes the light waves move in different directions. With polarization, light transmission is oriented in a single direction, making it more predictable and less random.

How do polarizing filters work? 

Polarizing filters work by cutting out the reflected light that travels at specific angles. This reduces reflections, glare and haze awhile enhancing color saturation, contrast and intensity. These filters are especially revered by anyone who shoots images of vegetation, water surfaces or blue sky.

Shot without a polarizing filter.
Shot with the Urth CPL Polarizing Filter Plus+

When a circular polarizing filter is on the end of your camera lens, you can easily and conveniently turn it. This lets you modulate light exposure levels, giving you more control over shutter speeds especially when working with long exposures

Many people assume it’s the filter’s shape that determines whether it’s a CPL or a linear polarizer. But, this isn’t the case at all. In fact, both filters are circular and look the same. When used appropriately, they both deliver the same fantastic image-enhancing results for your photography.

The actual difference between these polarizing filters is in their specific polarization effects and how they each modify light waves that pass through them.

The two types of polarization

Linear polarization refers to when you polarize light vertically or horizontally. Therefore, a linear polarizing filter only allows horizontal or vertical light waves to enter the filter when it is rotated.

Circular polarization relates to light waves that move in a circular direction, leading to left-handed or right-handed polarization. A circular polarizing lens filter, or CPL, therefore, filters circularly polarized light. But, it is also sensitive to linear polarized light.

A CPL filter is basically a linear polarizer, but with an extra optical glass element behind it. This glass is called a quarter wave plate, and it circularly polarizes light. When light hits the light meter, it gives accurate exposure results.

How to decide whether to buy a CPL or linear polarizing filter 

Whether you choose a CPL filter or a linear polarizer is largely down to the type of camera you own. In general, CPL filters are more versatile than linear types. CPL filters are suitable for all digital cameras, but a linear polarizer won’t work on DSLR cameras.

If you own a modern DSLR camera, it will probably have a partially reflecting mirror. The presence of this partially reflecting mirror can cause metering errors if you use a linear polarizer with a DSLR camera. A CPL filter does not interfere with the lens metering system, however, so is the right choice of polarizing filter for a DSLR camera.

If you own an old compact camera that is unlikely to have a partially reflecting mirror but instead has a fully reflecting mirror to reflect all polarizations with equal density. You can use both linear and circular polarizing filters with these.

Linear polarizers also cause problems with autofocus, and sometimes issues arise when sticking them on extremely wide angle lenses.

Polarizing filters can also darken the sky in ways similar to UV filters, although they don’t block out as many stops of light as neutral density filters do.

Check your camera manual if you’re not sure which filter to use for your camera type. Whether you choose a CPL or linear polarizer, always buy good quality polarizing filters from a reputable source, to ensure the best image-enhancing results.

Wrapping Up

Circular and linear polarizing filters each have their own unique advantages and use purposes, and it’s really up to you to decide how to use each to your strengths and adapt their many benefits to your creative process. 

If you’ve been thinking about picking up your first polarizing filter, have a look at Urth’s line of polarizing filters, all made with premium optical glass and guaranteed to help take your photography to the next level.

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2021-09-22T04:28:21+00:00Categories: Gear|Tags: , |