An ND filter reduces the amount of light entering your camera without changing color or focus

An ND filter (neutral density filter) is a piece of glass or resin you screw onto the front of a camera lens. It works like sunglasses for your camera — it makes everything darker so less light reaches the sensor. The word "neutral" means it darkens the image evenly across all colors, without shifting the picture toward blue, orange, or any other tint.

The main reason to use one is to let you shoot with a wider aperture or slower shutter speed in bright conditions. Without an ND filter, bright sunlight forces you to use a fast shutter speed (like 1/2000th of a second) or a small aperture (like f/16), which limits your creative choices. An ND filter lets you ignore the brightness and set your camera the way you actually want to.

ND filters come in different strengths, measured in stops. A 1-stop filter cuts light in half. A 3-stop filter cuts it to one-eighth. A 10-stop filter cuts it to about one-thousandth. The stronger the filter, the more you can slow down your shutter speed or open up your aperture.

Key Takeaways

  • An ND filter darkens your image evenly so you can use a wider aperture or slower shutter speed in bright light.
  • ND filters are measured in stops — a 3-stop filter is stronger than a 1-stop, and a 10-stop is stronger still.
  • Common uses include blurring moving water, keeping backgrounds blurred in daylight, and shooting video with a cinematic look.
  • ND filters screw onto the front of your lens and work with any camera that accepts them, from smartphones to professional DSLRs.

How ND filters change what you can shoot

In bright sunlight, your camera's sensor is very sensitive. If you want to blur the background (which requires a wide aperture like f/2.8), the image will be overexposed — too bright to see detail. An ND filter darkens the scene so you can open the aperture without overexposure.

The same applies to shutter speed. If you want to photograph a waterfall and blur the flowing water into a smooth, silky effect, you need a slow shutter speed — maybe 2 or 4 seconds. In daylight, that shutter speed would overexpose the image. A 10-stop ND filter lets you use that slow speed without the image washing out.

Video shooters use ND filters for a different reason. Video cameras work best with a shutter speed around 1/50th of a second (for 24fps footage). In bright daylight, that shutter speed overexposes the image. An ND filter lets you keep that shutter speed and get the cinematic motion blur that video audiences expect, instead of the jerky look of a faster shutter speed.

Types of ND filters and how they differ

The simplest ND filters are fixed-strength — they come in one darkness level, like 3-stop or 10-stop. You buy the one you need for your most common situation. They are cheap, small, and produce no image quality loss.

Variable ND filters let you rotate a ring to adjust the darkness from, say, 2 stops to 8 stops. This sounds convenient, but they have a real drawback: at extreme settings, they can create an X-shaped pattern across your image (called an "X-effect"). They also cost more and are thicker, which can cause vignetting — dark corners — on wide-angle lenses.

ND filters also come in different materials. Glass filters are standard and work well. Resin filters are lighter and cheaper but scratch more easily. Some photographers use stacked filters — screwing multiple fixed ND filters together — to reach very high stops (like 20 stops for extreme long-exposure photography).

What strength ND filter to choose

A 1-stop or 2-stop ND filter is useful if you mostly want to shoot with a wider aperture in daylight. It is subtle and works in many situations. A 3-stop filter is a good middle ground — strong enough to blur water or keep backgrounds soft, but not so dark that you need a tripod for every shot.

A 10-stop filter is for serious long-exposure work: silky waterfalls, blurred clouds, empty streets. You will need a tripod because the image is very dark and your shutter speed will be several seconds. A 10-stop filter is also popular with video shooters who want to maintain a cinematic shutter speed in bright sun.

If you shoot in variable light — sometimes sunny, sometimes cloudy — a variable ND filter might make sense despite its drawbacks. If you mostly shoot in one type of light, a fixed filter of the right strength will give you better image quality and cost less.

How to use an ND filter

Screw the filter onto the front of your lens, just like a lens cap. If your lens has a filter thread size (usually printed on the barrel or in the manual), buy an ND filter that matches that size. Common sizes are 52mm, 58mm, 67mm, and 77mm.

Once the filter is on, your camera will see a darker image. Your light meter will adjust automatically — your camera will suggest a slower shutter speed or wider aperture to compensate. You can then adjust further to get the effect you want.

One important note: autofocus can struggle in very low light (like with a 10-stop filter). If your camera hunts for focus or fails to lock, switch to manual focus. This is especially common with video cameras and telephoto lenses.

ND filters for phones and compact cameras

Smartphone cameras have fixed, small apertures (usually around f/1.5 to f/2.8) and tiny sensors, so they do not benefit from ND filters the way DSLRs do. However, some phone users attach clip-on ND filters to blur water or reduce glare. These are inexpensive but produce lower image quality than a dedicated camera filter.

Compact cameras and mirrorless cameras with small sensors have the same limitation — the aperture is already small, so an ND filter mainly helps with long-exposure effects. If that is your goal, it is worth trying. If you want to blur the background, an ND filter will not help much on these cameras.

Common mistakes with ND filters

The most common mistake is buying the wrong filter size. Check your lens barrel or manual for the filter thread size before you order. Buying a 77mm filter for a 52mm lens means it will not fit.

Another mistake is stacking too many filters. Each filter adds a small amount of reflection and glare, especially at the edges. If you stack three or four filters, you may see a loss of sharpness or contrast. If you need a very strong filter, buy a single 20-stop filter instead of stacking.

A third mistake is forgetting to remove the filter when you are done. ND filters are easy to forget about because they do not change the look of the image — they just darken it. If you switch to indoor shooting and forget the filter is on, your images will be underexposed.

Frequently Asked Questions

Do ND filters work on all lenses?

ND filters work on any lens with a filter thread on the front. Most modern lenses have one, but some older lenses and specialty lenses do not. Check your lens barrel for a size like "52mm" or "77mm" printed near the front. If you see that, the lens accepts filters.

Will an ND filter reduce image quality?

A good glass ND filter has minimal impact on sharpness or color. Cheap filters and resin filters can introduce slight softness or color shifts. Stacking multiple filters or using a variable ND at extreme settings can reduce quality more noticeably. For best results, buy a single fixed-strength glass filter from a reputable brand.

Can I use an ND filter indoors?

Indoors, there is usually not enough light to justify an ND filter. The filter will make the image darker, forcing you to use a slower shutter speed or wider aperture — the opposite of what you want. ND filters are designed for bright outdoor conditions.

What is the difference between an ND filter and a polarizing filter?

A polarizing filter reduces glare and reflections and makes colors more saturated. An ND filter simply darkens the image. They do different things. Some photographers use both together, but they are not interchangeable.

How much should I spend on an ND filter?

A decent fixed-strength glass ND filter costs between $20 and $80 depending on the lens size and brand. Variable ND filters cost $40 to $150. Expensive does not always mean better — mid-range filters from established brands like B+W, Hoya, or Tiffen perform well. Avoid very cheap filters, which often have color shifts or poor optical quality.