What is a CPL Filter?

A CPL lens filter, also known as a circular polarizing filter, is a very useful camera tool. It helps enhance photos by reducing reflections. It also makes colors more vivid and improves overall image quality.

This filter blocks specific light to show clear skies and water. It effectively reduces glare on shiny surfaces to capture more details in your photos. Vantrue dashcams also utilize a CPL lens filter to reduce windshield glare for clearer videos.

How Does a CPL Lens Filter Work?

CPL filters use polarization to change the way light behaves. Light waves move in many directions. When they bounce off a surface like water or glass, they align in one direction.

CPL filters have two parts to handle this light. First, the linear polarizer blocks unwanted light waves and lets only aligned ones through. Next, the quarter wave plate turns the light into circularly polarized light. This allows it to play nicely with your camera's focus and lighting systems.

The filter works best when the light is hitting it at a specific angle. For example, if your camera is at a 90-degree angle to the sun, the filter will work best. This angle helps reduce reflections and makes photos clearer.

Rotating a CPL filter is key to controlling its effects. The filter has a ring that you can rotate to adjust the amount of light that comes in. This lets you control glare or make colors in your photos stand out more.

The rotating part has two main components. The linear polarizer rotates to match the angle of the light, while the quarter wave plate keeps the light circularly polarized. Together, they let you control how the filter works.

There are many reasons why CPL filters are superior to linear polarizers. Linear polarizers mess with your camera's focus and light system. CPL filters solve this problem by turning linear light into circular light. This makes them work better with modern cameras.

CPL filters are also more flexible. You can turn the filter to change how it affects the light. This gives you more control over your photos. Whether you're shooting landscapes or reducing glare, CPL filters can help you get the best results.

Pro and Cons of CPL Filters 

Effects of a CPL Filter on Photography

Reduce Reflections

The CPL filter helps eliminate reflections from shiny surfaces like water or glass. It blocks certain light waves that cause glare. This way, you can see the reflections clearly or eliminate them completely. For example, when taking photos of lakes, the filter can reduce glare from the water. This can reveal details beneath the water's surface, making the photo clearer and more interesting.

It also works well when shooting through windows. Without a filter, reflections would block your view. By adjusting the CPL filter, you can reduce these reflections and focus on what's outside. This is especially useful for landscape photos, where reflections can ruin the natural beauty.

Enhance Color and Contrast

The CPL filter makes colors brighter and increases the contrast of your photos. It blocks excess light, making colors like blues and greens stand out more. For example, in a forest, it can remove the shiny white light caused by sunlight on leaves. This makes the greens look smoother and more natural.

The filter can also improve contrast by separating objects in a photo. It makes the foreground stand out while keeping the background sharp. This creates a balanced and professional looking image. This effect works best with outdoor photos, as sunlight can make colors appear dull.

Darkening Skies for Dramatic Effects

A CPL filter can make skies look darker and more dramatic. It reduces scattered light, making the blue sky deeper and the clouds stand out more. This adds a bold and polished look to your outdoor pictures.

The effect works best when the sun is at a 90-degree angle to your camera. At this angle, the filter is most effective, giving you the best results. Whether it’s a sunset or a bright day, this feature helps create stunning photos with ease.

Tip: Turn the CPL filter to find the best angle for darkening skies. Small changes can greatly improve your photo.

Effects of a CPL Filter on Car Dash

CPL filters aren’t just for traditional cameras, they’re also a revolutionary addition to dash cams, including models like the Vantrue. These filters are designed to eliminate windshield glare, a common problem that can obscure important details in your footage. Bright sunlight or reflections from your dashboard can create a distracting glare, but CPL filters help reduce it for clearer, more usable video.

Simply screw the CPL filter onto your dash cam lens. Vantrue dash cams easily accommodate these filters.

The Vantrue 40mm CPL filter is for use with Vantrue E1, E1 Lite dashcams, E2, E3, N4 Pro, N5, N2X, S1 Pro front-facing lenses. NOTE: It will not work with other Vantrue dashcams.

Read more: Types of Dash Cams

Practical Tips for Using a CPL Filter

To use your CPL filter well, adjust it carefully. First, make sure it’s tightly attached to your lens. A loose filter can ruin your photo quality. Use the right filter size to match your lens. If the size is wrong, the edges of your photo might turn dark.

After attaching, turn the filter to find the best angle. The filter works best when the sun is at a 90-degree angle to your camera. This angle reduces glare and makes colors brighter. Try different angles to see what looks best. For example, turning it slightly can make skies darker or make reflections disappear.

Knowing how polarization works helps you use the filter better. Light moves in many directions, but the filter blocks unwanted light. By turning the filter, you control how much light enters. This gives you more creative options for your photos.

Avoiding Common Problems

Using a CPL filter incorrectly can mess up your photos. One mistake is not turning the filter correctly. This can cause uneven effects, like dark spots in the sky. These spots look unnatural, especially in wide-angle shots.

Another problem happens with ultra-wide lenses. Lenses between 18mm and 20mm can create halos or uneven skies. Test your filter with your lens before taking important pictures to avoid this.

Some people think all CPL filters are the same, but they’re not. Cheap filters might not work well. Always check if the filter fits your lens. Don’t screw it on too tight, as this can damage your lens or the filter.

FAQ

How is a CPL Filter Different From Other Filters?

A CPL filter blocks polarized light to cut glare and boost colors. Unlike UV or ND filters, it changes how light hits your lens. This makes it great for outdoor photos with bright skies and less glare.

Why Do CPL Filters Make Photos Darker?

CPL filters block some light, which makes photos less bright. They filter out certain light waves to improve image quality. To fix this, adjust your camera settings, like raising the ISO or slowing the shutter speed.

Can I Keep a CPL Filter on All the Time?

No, you shouldn’t leave it on always. CPL filters block light, which isn’t good for low-light photos. They also change reflections, which might not work for every picture. Use them for outdoor shots or glare reduction, and remove them indoors or in dim light.

Why Do CPL Filters Create Uneven Skies With Wide Lenses?

Wide-angle lenses show more of the scene, so CPL filters polarize light unevenly. This makes some parts of the sky look darker than others. Test your filter with your lens to avoid this problem.

How Can I Tell If My CPL Filter Is Working?

Turn the filter while looking through your camera. You’ll see changes in reflections, colors, or sky darkness. When you see the effect you want, the filter is working. Try different angles to get the best shot.