K&F Concept GND Nano-Xcel Series circular filters review: ND grads without the big and bulky holders

Most of the best Graduated Neutral Density filters (aka ND grads or GND filters) are of the slot-in variety, but these circular ND grads screw directly into your lens's filter thread without the need for additional holders. But what they gain in portability and convenience, they lose in flexibility; the graduated transition area is fixed at the center of the filter.

There's a choice of two filter strengths, offering a three- or four-stop difference between the clear portion and darkest area of the filter. There's no hard graduation on offer, so the transition from light to dark on offer here is better suited to more undulating horizons, such as rolling hills, buildings, or mountains, rather than seascapes.

K&F Concept is known for producing quality photographic accessories for award-winning products at budget prices, so I was very keen to see how this budget-friendly screw-in GND filter fared against its slot-in competition. Here’s how I got on…

K&F Concept GND Nano-Xcel circular filters: Specifications

K&F Concept GND Nano-Xcel circular filters: Price

The K&F Concept GND screw-in filters are available in GND8 or GND16 varieties, blocking out 3 or 4 stops of light at their darkest areas, respectively. They’re also available in no fewer than nine sizes for different filter threads. As is typical with round screw-in filters, the larger the thread diameter, the more you pay. In the US (other territories have similar pricing and reductions), the smallest 49mm version normally costs $56.99 for the GND8 version, though it was on sale at the time of review for $49.99. The largest GND8 is the 82mm fit, which costs $78.99, but was reduced to $69.99.

What was a little odd was that the stronger GND16 is less expensive, with its 49mm version costing $58.99, reduced down to just $31. While its largest 82mm iteration costs $75.99, it was on sale for a bargain $39.99 at the time of writing. Our price-finding widget will find the best current prices for you!

The filters are good value for money, especially if you can pick them up at a sale price, and offer a competitive set of features. They’re also very lightweight, compact, and portable. However, if you’re serious about your landscape photography, you may want to consider a square filter system, such as K&F Concept’s X-Pro system, as this will give you much more flexibility when it comes to lining up the horizon anywhere other than in the center of the frame, and also enables the stacking of filters together with lessened danger of vignetting, as we'll see below.

K&F Concept GND Nano-Xcel circular filters: Design & Handling

K&F Concept imports its optical glass from Japanese optical glass specialist AGC and employs a 28-layer coating to help make the filters more resistant to water and scratches. This coating is also double-sided, which is a nice touch and makes it easier to clean.

The glass filters are housed in a circular frame made of aviation-grade aluminum and come with filter threads from 49mm to 82mm. However, I would always suggest buying the version that fits your largest-diameter lens and using stepping rings to work with your smaller lenses. This is not only cheaper than buying individual filters for each of your lenses, but it also cuts down on space and weight in your kit bag. The filters come with a small, round plastic hard case, which doesn’t take up much space in your kit bag.

The filter frame is CNC-precision-carved and 7.5mm deep, though it only protrudes by 5mm when mounted on your lens. The filter is made up of two rings: the rear one is knurled to give you good purchase when screwing it into the front filter thread of the lens, while the front ring rotates freely and is partially knurled to help you grip it when rotating the filter to line up the gradient with the horizon in your images.

While this enables both landscape and portrait-format images, or off-kilter angles, the drawback of this design is that the graduation has to be bang in the center of the scene, so creative compositions, such as placing the horizon according to the rule of thirds, are out.

The K&F Circular GND filters are only available in soft gradients and only come in GND8 and GND16 options, blocking three or four stops of light, respectively. If you’re after GND filters with a different strength, hardness, or with the ability to move the gradient up and down, then you’d be better off looking at K&F Concept’s Nano Xcel Pro range of GND filters and a dedicated filter holder.

K&F Concept GND Nano-Xcel circular filters: Performance

The GND8 and GND16 soft filters belong to K&F Concept’s Nano X Series, the company’s flagship line of filters for 'superior optical performance'. This means we see the CNC-precision-carved 'anti-slip' teeth on the aluminum frame, Japanese AGC glass, and a nanotec coating.

Let’s start with the coatings. While it's not quite the 36 multilayered coatings we’re treated to on some other K&F Concept Nano X filters, we still get a respectable 28 layers designed to tame reflections and color casts, in addition to making the filters waterproof, and scratch- and oil-resistant. K&F Concept claims that its GND8 and GND16 filters have reflectance of just 1.25% and 1.5%, respectively, while competing filters generally range between 2% and 4%.

K&F’s nanocoating is hydrophobic, so water beads off it nicely, with droplets easily shaken off. It also makes them easy to clean, as water and grime don’t tend to stick to the glass surface. I also dragged a sharp nail over the surface of the filter to test its scratch resistance, and I couldn’t inflict a mark, even when pressing hard, so it’s a very tough, hardy filter. It also survived a drop onto concrete from 1.5m, and only a slight scuff to the metal filter frame could be seen – the all-important glass remained intact.

Image quality is said to be ‘lossless’, while '8K Ultra HD' is written on the box – I suppose this means it can support video-recording in 8K resolution without any downgrading of the image. Indeed, when zooming in on the images taken with my 45MP Canon EOS R5, I saw fantastic sharpness and color reproduction.

Many screw-in filters are about 3mm deep when mounted, and slimline options are even thinner. However, this one is quite deep to accommodate the secondary ring that twists to turn the filter gradient, protruding by about 5mm when mounted. While I didn’t see any vignetting when shooting with my 15mm ultra-wide-angle lens on a full-frame body, this would make vignetting more likely when stacking multiple filters. For example, if you wanted to use a 10-stop ND filter to add motion to the scene, as well as a GND to retain detail in the sky.

What I did notice, though, was that while the ring to rotate the filter to line up the gradient with your horizon was easy enough to use, it did mean I'd often inadvertently overtighten the main mounting ring to my lens, which usually meant it was pretty solidly stuck on the lens, requiring force when it came time to take it off again.

The overall performance was very impressive for the price; however, its biggest drawback is due to the nature of screw-in filters. You’re hamstrung on your compositions by having no option but to place your horizon slap-bang in the middle of your scene. This only goes to highlight the clear advantage of a slot-in filter system when it comes to ND grads, although this is admittedly bigger and more expensive.

K&F Concept GND Nano-Xcel circular filters: Verdict

Considering the low price of these filters, the K&F Concept Soft GND8 and GND16 offer a lot of filter for your money and would be a great place to start if you’re just getting into landscapes using graduated ND filters.

More advanced enthusiasts and pros will quickly find the limitations of the screw-in style, which does compromise how creative you can get with compositions, as the horizon needs to be in the middle of the frame to work with these screw-in filters.

That being said, these filters belong to K&F Concept's top-tier Nano-X series and, as such, have brilliant image quality and coatings that can’t be faulted. For travel photographers on a budget and looking to travel light, this is a good option.

Alternatives

Marumi Magnetic Graduated ND Filters offer good value and employ a novel magnetic clip-on system that allows quick attachment and detachment to their filter holder. They will be a hit with those who like to work fast.

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Designed for use with the LEE100 system for full-frame cameras, these LEE100 Neutral Density Grads are the bigger brothers of the LEE85 range for compact cameras with smaller lenses, and boast the same lightweight resin design.

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