Learn About Neutral Density Filters

An image at sunset of sea water rushing through the rotted pylons of a collapsed dock
Neutral density (or ND) filters reduce the amount of light that passes through the lens. This gives the photographer more control over the shutter speed and aperture to produce effects like the smoothing of water, to shallow depth of field or to show the movement of clouds.

ND Filter Basics

An image of a rushing brook through a rocky river bed covered in leaves lined by mid autumn trees
Formatt Hitech Neutral Density filters are colorless filters that remove light evenly across all spectrums. Neutral density filters are used to lengthen exposure time, or allow the shooter to use a larger aperture. Common uses are:
  • Creating shallow depth of field during daytime
  • Making water appear misty and ethereal
  • Removing people from busy areas
  • Transforming clouds and skies

What is Filter Density

ND filters are available between 1-10 stops of density, plus 13 & 16 stops for long exposure. The density of the ND is written either in the number of stops, or using the traditional density scale.
  • 0.3 = 1 stop
  • 0.6 = 2 stops
  • 0.9 = 3 stops
  • (etc)
Be careful to note the difference. For example, a 6 stop filter could be labeled “1.8”, but a two stop filter could be labeled “0.6.”

Popular Uses for ND Filters

Three Formatt Hitech Firecrest Neutral Density filters lined up according to desity strength

  • 3-4 stop ND filters allow street photographers to shoot their fast lenses “wide-open” even during the middle of the day.
  • 4-6 stop ND filters create a moderate lengthening of exposure time to create a misty effect in moving water. Usually around 1 second.
  • 6-10 stop ND filters create 2-30 second exposures that are perfect for waterfalls, streams, and seashores.
  • 13 stop ND filters are used to create ethereal effects in water and clouds, with exposure times around 2 minutes in duration, especially in areas where clouds are moving quickly (such as coastal cities).
  • 16 stop ND filters are used to create the long exposure effects - such as streaky clouds and flat water - that have been popularized by photographers such as Joel Tjintjelaar. 16 stop filters allow the photographer to make 5-8 minute exposures, even during mid-day lighting conditions.

What is Filter Density

ND filters are available between 1-10 stops of density, plus 13 & 16 stops for long exposure. The density of the ND is written either in the number of stops, or using the traditional density scale.
  • 0.3 = 1 stop
  • 0.6 = 2 stops
  • 0.9 = 3 stops
  • (etc)
Be careful to note the difference. For example, a 6 stop filter could be labeled “1.8”, but a two stop filter could be labeled “0.6.”
Three Formatt Hitech Firecrest Neutral Density filters lined up according to desity strength

Choosing an ND Filter

Firecrest ND

A rectangular formatt hitech neutral density filterFirecrest NDs are glass filters that use a technologically advanced rare-earth metal coating to create the most neutral filters in the world. Firecrest ND coating is a huge technological advancement when compared to any previous generation ND filter. Firecrest ND filters feature an almost perfectly even absorption of light across all spectrums (including UV and infrared) resulting in hyper-neutral NDs at all densities. In fact they’re so neutral, that for the first time we can create 13 and 16 stop densities in a single filter without significant color cast. Clearly, the advantage of Firecrest is most evident at the darkest densities, such as 10, 13 and 16 stops.

Because the ND effect comes from the coating itself, we’ve gone to great lengths to protect it. On our rectangular filters the coating is sandwiched between two pieces of bonded glass. This protects the coating completely and allows us to lap and polish the filters to the highest tolerance in the industry, meaning your filters will have the lowest possible distortion. On our circular filters, the coating is featured on the outside of the filter because the ring protects the filter. This allows us to add anti reflective and hydrophobic coatings to the outside of our circular filters.

Firecrest filters are available between 1-10 stops of ND, plus 13 and 16 stops for long exposure.

Standard ND

A square formatt hitech standard resin 1.2 neutral density filterStandard ND filters are professional quality resin ND filters available between 1-4 stops of ND. Standard NDs don’t block infrared, but they only go up to 4 stops of density, so infrared is not an issue because there is not enough filter factor to overwhelm the digital sensor. With standard NDs, you get a professional quality ND at a really low price.

Variable ND

Two Formatt Hitech round threaded Variable ND filters side by side. One is set at minimum light reduction and is see through, the other is set to maximum light reduction and completely opaque to the naked eyeVariable ND filters work between approximately 2-6 stops. Variable NDs are actually two polarizers that counteract each other to create the ND effect. Meaning there is a slight polarization effect. For DSLR filmmakers working quickly the Variable ND is a terrific tool.

ND Filter Variations

An image from atop a hill looking down over a dense forest with a lake inside. Beyond the forest are grassy fields separated by hedges. The slightly cloudly sky is lit up for the near sunset light

ND filters are also available as grads or graduated ND filters. These filters provide the ND effect on a selected part of the scene. The most common use of a grad filter is to reduce the luminance of a bright sky to match the terrain below.

Three Formatt Hitech Graduated IRND filters lined up according to desnity strength