Field Testing Breakthrough Photography’s X4 ND and Dark CPL Filters

Neutral density filters. They are one of the mainstays of modern outdoor photographers. Look in any pro’s or serious hobbyist’s gear bag and you’re virtually assured to find at least one, if not more, ND filters.

I like a good analogy as much as the next person, and one of my favorites concerns calling ND filters “sunglasses for your camera.” Feel free to use that line.

ND filters block out light which allows us to use longer exposures in conditions which would normally be far too bright. This enables motion blur and other dynamic characteristics to be present in your photos when they otherwise might not be possible. But not all ND filters are created equal. Generally, the case exemplifies the “you get what you pay for” notion that with higher cost comes a higher grade product in terms of build and optical quality.

X4 ND Build Quality

The X4 ND filters continues the same extreme performance as the X3 Series. For this review, I evaluated X4 ND filters with darkening grades of 3-stop, 6-stop, and 15-stop in a 77mm size. The majority of the images shown here display the 3-stop filter.

The construction of the X4 ND consists of a brass housing which holds a SCHOTT Superwite B270 optical glass element. There is a heft and solidity to the ND that is completely comforting. It is seemingly built for consistent professional use. The outside circumference of the filter sports deep cut “traction” ridges that superb gripping of the filter wet conditions or with gloved fingers.

Each side of the element is layered with eight coats of MRC (multi-resistant coating) which is an ultra hard hydrophobic substance that reduces glare and protects the filter element from dirt and moisture intrusions. The MRC16 (8+8 coats) nano coating is stated by the manufacturer to be physically harder than the glass of the filter itself. In my tests the water drops and dust particles can essentially be “blown off” the filter easily without the need for a lens cloth*. The MRC16 coatings, at least from a practical standpoint, seem to produce the kind of results stated in the product description.

X4 ND Sharpness, Color Cast, and Vignetting Results

It’s somewhat paradoxical that some of the strongest attributes of the X4 ND give me virtually nothing to write about at length. Breakthrough Photography market’s these as the “Worlds Sharpest ND Filter. 100% Guaranteed” and also as “…the most color neutral ND filter for the discerning landscape photographer”.

That simply is what the X4 delivers. There is no evident color casting observed in my tests. The sharpness? Every filter I’ve used in the X3 line up, and now the X4 Series, has offered incredible sharpness. The image quality produced by the X4 ND is quite literally second to none.

Vignetting is a common problem when using any type of light blocking photography gear. Darkening at the peripherals in both filters and lenses is just an accepted downside to our tradecraft at times. That being said, the X4 ND filters seem to be completely free of vignetting while being used with my semi-wide angle test lens (Sigma 24mm f/1.4) and full frame camera (Sony a7R Mk1). Even with the darkest X4 ND (15-stop) currently offered, there was virtually no discernable darkening at the edges of the frame caused by the filter. Here are three unedited images showing the 15-stop X4 ND in use.

X4 Dark CPL

Life occasionally offers us little bonuses. At the time I was being sent the X4 ND filters for this evaluation, Breakthrough Photography was developing a brand new “Dark CPL” filter. As a result, I was fortunate enough to also be able to include this prototype 82mm Dark CPL as part of this review.

CPL stands for circular polarizer. Just as with the ND filters, a quality polarizing filter is a mainstay of the professional outdoor photographer’s tool set. Polarizing filters essentially straighten lightwaves so that reflections and glare are minimized. Polarizers also serve to darken skies and make color tones appear more vibrant. Circular polarizers take this a step further by allowing the user to literally dial in the amount of polarization desired simply by rotating the bezel of the filter housing.