Review of the Breakthrough Photography X4 CPL Circular Polarizing Filter

Make no mistake, this is, in fact, a review of the X4 Circular Polarizer from Breakthrough Photography. That being said, the entire subject requires a little bit of photographic geekiness in order to grasp the full understanding of the product being reviewed. So, if you absolutely don’t want to add any more brain wrinkles feel free to skip the next couple of paragraphs. If you do skip…shame on you.

Geeky stuff about polarizers

Polarizers – we’ve all heard of them and the majority of us photographers have used them extensively from one time or another. How do they work? And more importantly, how do you know when you’ve found a good one?

These are all great questions and oddly enough these things aren’t always well known by even some experienced shooters. Polarizers are just filters. These filters work to sift out polarized light which commonly occurs in our photographs from reflections and glare. The noticeable byproduct of this filtration is the reduction of said reflections and glare as well as the deepening of colors and most noticeably, the darkening of the sky.

Polarizers come in two flavors: linear and circular. It’s somewhat of a weird concept as all polarizers are in fact linear…but not all linear polarizers are circular. That might sound slightly cryptic but that is not the intention.

At their most basic definition, the way polarizers work is to filter our non-linear rays of light. Circular polarizers further enhance this effect by adding what’s called a quarter-wave plate to the camera side of the linear polarizer. The quarter wave plate serves to essentially convert the incoming light into a helix and the polarization effect can then be dialed-in to whatever degree is needed. This is of great benefit because the majority of SLR and DSLR cameras are sensitive to polarization and linear polarized light can cause internal camera metering to malfunction.

The X4 CPL Circular Polarizing Filter

Now that you’ve had a crash course in how circular polarizers work, it’s time to talk about the X4 CPL Circular Polarizing Filter by Breakthrough Photography. This will be my fourth time evaluating filters by the folks at Breakthrough. With each piece of gear I have been consistently impressed with the build and optical quality to such an extent to where I find it difficult to list any faults. The X4 CPL is no different.

Breakthrough Photography currently markets this polarizer as being the “world’s most advanced circular polarizer” so I put the X4 CPL Circular Polarizing Filter to the test to see just how this claim holds up in real-world shooting.

Build Quality

The construction of theX4 CPL Circular Polarizing Filter is blackened brass, much like their line of X4 ND filters. The filter housing is robust and feels extremely sturdy. Deep traction grooves are cut around the bezel and provide for a solid grip even with gloved or wet hands.

An interesting property of brass is that unlike other metals such as aluminum it is non-galling. This means that it is less likely to bind and become stuck when stacking multiple filters. The filter bezel turns quite smoothly when engaging or disengaging the polarization effect.

The optical element is made from SCHOTT Superwhite B270® optical glass. Each side of the glass is then treated with eight layers of Breakthrough Photography’s proprietary nanotec® and MRC (multi-resistant coatings) optical coatings which cause dirt and moisture to essentially slide right off of the glass itself.

Overall, the build quality of theX4 CPL Circular Polarizing Filter is exceptional and it looks great to boot. The company also backs the filter with a 25-year guarantee.

Optical Performance

Of course, the real question about the X4 CPL concerns its optical quality, which in turn will greatly impact the final quality of your finished photographs. When it comes to photography filters, the sharpness, vignetting, and color cast, are the three main points of interest for most photographers.

While it’s great to talk about all these points actual test images speak louder than words. So have a look at the sample images as you read my thoughts on the results and judge for yourself.

Sharpness

In terms of sharpness, the X4 CPL exceeds all expectations. No image degradation was observed even at the maximum strength filtration.

To left is the image without the X4 CPL applied. The image at the right is with the X4 CPL. Both zoomed to 1:1 for comparison.

Images remained crisp and detail was not lost due to the addition of the filter.

Color Cast and Vignetting

A common problem seen with polarizers and most filters, in general, is the unwanted color casting sometimes encountered. The color cast happens due to the coloration of the optical glass and often worsens in lower quality filter systems.

An image with a high color cast from an ND filter. Low-quality polarizers can carry the same effects.

The images produced by the X4 CPL seem to be completely free of this discoloration just as they are advertised. No discernible color cast was observed in any of the test images I made using the filter.

The same is true for vignetting. Darkening of the corners of the photos was not observed even at the strongest filtration setting.

Final Thoughts on the X4 CPL

There’s a certain feeling of uneasy optimism which begins to surface whenever I come across gear which does not seem to have any obvious weak points.”Have I missed something? Is this really that good?”

Having reviewed multiple pieces of kit from Breakthrough Photography I can say that they have consistently produced insanely high-quality photographic gear that is innovative, sturdy, and relatively cost-effective. I use quite a few of their filters in my own personal photography work and have put them into environments from Death Valley to the coast of the Atlantic Ocean and everywhere in between (or least it seems).

The X4 CPL has thus far given no reason for me to believe that its quality would not serve any serious photographer’s needs for years to come. The build quality is heavy-duty and the image quality, especially sharpness, is outstanding. It retails for $129-159 USD (depending on filter size) at the time of this review. Find out more details about the X4 CPL here, or shop Amazon for the size you need here.

Rating 5/5 stars – my first ever! 

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