Do you need one of the best neutral density filters? If you're experimenting with long exposure photography then the answer is probably yes.
Little more than dark glass, neutral density filters (aka ND filters) are designed to control light. They purposefully reduce the amount of light that reaches your camera lens and, therefore, your camera's sensor. That means you can open the shutter for longer.
So with an ND filter, you must use shorter shutter speeds to get the same image. Why would you want to do that? Usually, it's to capture motion. Those beautiful milky water images of waterfalls that you've seen all over Instagram are created using an ND filter. They're also commonly used to create other kinds of motion blur images such as traffic trails, streaky clouds and ghosted images of crowds, as well as for creating a shallow depth of field while working in bright conditions. Some kinds of ND filters can also be used for nightscape astrophotography.
If you're just starting out with ND filters then a great way to get yourself educated and experienced is to invest in a good value set like the Hoya ProND filter kit. Each filter in this three-pack are all made using anodized aluminum and has an ACCU-ND coating that creates a neutral color balance.
Comprising 3-stop, 8-stop and 10-stop filters, all three screw-in to the thread of a lens, making it a time-consuming process to swap between them. Since the alternative is to use square filters and a bolt-on filter holder you could argue these are more convenient to pack, though trickier to swap between. Either way, the filters themselves are mid-range, offering great build quality and image excellence for the money. They're also available individually in myriad sizes and strengths.
These ND filters are designed to slip into all kinds of square filter holders, from 75mm through 180mm. Aside from the convenience of filter holders, their trick is to use nano-coated glass designed to repel water, oil and dirt while reducing the wavelengths of visible light entering your camera without altering the brightness, color or contrast. We're talking high-quality glass, though do expect some color cast. As a bonus, NiSi offers an Exposure Calculator app for smartphones that makes short work of calculating shutter speeds when using these ND filters (something that can be a bit of a head-scratcher, to begin with) and even adds an in-app exposure timer.
ND filters that come with a smartphone app? It's a novel idea, but with a built-in exposure timer and notifications, it helps take the math out of using these excellent ND filters. However, square ND filters like the LEE Filters 100 x 100mm ProGlass IRND aren't for everyone. You'll need a 100mm filter holder — such as the LEE100 — and an adaptor ring for your lens.
It might all sound fiddly but actually makes the process of swapping between ND filters much faster than screw-in circular designs. Available in various strengths all the way up to 15 stops, Lee filters are about as advanced as they come, with the new ProGlass IRND glass offering accurate stop values, lots of contrast, clarity and accurate colors the reward for paying the admittedly high prices.
Cokin's range of ND filters is broad and, frankly, quite confusing. For newcomers, the smaller P-series is the cheaper place to start, but anyone looking for premium filters should invest a little more in the Z system. If you opt for the Z-Pro, which are the filters we've used and tested, then you'll need a holder to go with them, which is an additional $55/£50-ish outlay, and that's before you buy any adaptor rings or any actual filters. So, for landscapes, the best value for money is the ND creative kit, which comes with a holder, a selection of adaptor rings, a 2-stop full ND filter, a gradual 2-stop, and a hard 3-stop. These are perfect where you have a defined foreground and background and work well for things like light trails, night-time seascapes, and dramatic skies. You can also get landscape grad filters with colored glass, which can add real creativity to things like sunsets and deep-blue skies.
While you don't get the same weather-proofing as the NiSi range, you get excellent color reproduction, right through to the 10-stop ND1024. Each glass filter is tough, and comes with its own little pouch to keep the dust and scratches away. We love the adaptability of the system — the large holder fits most lens sizes once you have the right adaptor ring, and it's very effective at keeping light out of the edges — but we do find it quite fiddly actually to get onto the lens. A circular, screw-on ND filter system like the Hoya is far, far easier to use. So, if you're a serious landscape photographer willing to take your time with some serious glass, the Cokin Z-Pro system is highly recommended. If you favor ease of use and don't want to invest too much into filters you may not use as regularly, look elsewhere.
Since ND filters are often purposefully used close to waterfalls and on cloudy days it helps if they can deal with water droplets. Cue the B+W XS-Pro Digital ND MRC Nano, high-end ND filters that do something unusual with their multi-resistant coating. Able to fend-off water droplets — be that spray from waterfalls or just plain old rain — that coating also defends against dirt. Able to let through light while reducing reflections, its SCHOTT glass ups the color and clarity. The B+W XS-Pro Digital ND MRC Nano is sold in no fewer than 16 sizes, though only as circular screw-ons.
If you just want to dip your toes into the world of ND filters to see what it's all about then this low-strength filter set is the way to go. The Tiffen ND filter kit comprises three ND filters in 2 stop, 3 stop and 4 stop, which is enough to get you started taking better shots in bright light and indulging in some special effects-style shots with waterfalls and 'ghost' crowds. They also come with a nice carry case that makes it easier to keep them clean and protected. The less you pay for ND filters the more likely it is that the color balance in your finished images can be disrupted. However, that's not nearly as bad as it sounds since you can easily fix that in post-processing (just remember to shoot in raw).
How to use a neutral density filter
Why you can trust Space.com Our expert reviewers spend hours testing and comparing products and services so you can choose the best for you. Find out more about how we test and review products.
Although ND filters are little more than smoked glass, they can be fiddly to use. For starters, don't even think about using one unless your camera is on a tripod. That's because not only will you be taking long exposures, but you're going to further increase the time your shutter is open, so any movement within the shot is going to blur.
That's exactly what you want for your subject, but in order for that to have the desired effect, you're going to want to make sure everything else is in focus and sharp. That means using a tripod. However, actually achieving a sharp focus while your camera lens is wearing an anti-filter can be tricky. So it's best to compose your shot first and only then fetch the ND filter.
How to choose a neutral density filter
ND filters come in two distinct physical shapes and sizes; circular filters that screw onto lenses (do check the thread size in millimeters) and square filters that need to be used with a filter holder. Whichever style you favor you'll also need to specify which strength you want.
ND filters are sold in different densities — expressed as 'stops' — according to how much light they block (a 1-stop or ND2 halves the light, a 10-stop of ND100 just a hundredth). You're essentially paying for the quality of glass, with more expensive ND filters more likely to give you sharper images that retain accurate color.
Here at Space.com, we've cast our eye over the market for the best ND filters and rounded up the very best to suit all budgets. But if you're looking for a new lens to pair with an ND filter check out our guide to the best lenses for astrophotography or the best zoom lenses.