Neutral Density Filters Explained

What is a Neutral Density Filter, and what do you use it for?

A neutral density filter or ND filter – The purpose of a standard photographic neutral density filter is to reduce light entering the lens. Doing so allows the photographer to select combinations of aperture, exposure time, and sensor sensitivity, otherwise producing overexposed pictures. This is done to achieve effects such as a shallower depth of field and motion blur of a subject in a broader range of situations and atmospheric conditions.

Neutral density filters are often used to achieve motion blur effects with slow shutter speeds.

Examples of this use include:

Blurring water motion such as streams and waterfalls.
Reducing the depth of field.
Add motion blur.
Extend the length of the exposure.

You can photograph a waterfall at a slow shutter speed to create the milky water effect. You might determine that a shutter speed of five seconds will be needed. On a very bright day, there might be so much light that even at a minimum aperture, the five-second shutter speed would let in too much light and the photo would be overexposed. In this situation, you are applying an appropriate neutral density, allowing less light to come into the camera and enabling you to have a longer shutter speed.

Variable neutral density filter

The main disadvantage of neutral density filters is that you need to carry a range of different NDs to be entirely flexible in your shooting. This can become expensive. Manufacturers have created variable ND filters, an all-in-one type filter. These work by placing two polarizing filters together, one of which can rotate.

The advantages to this are that you get multiple ND filters in one package, saving money. Still, the disadvantage is a loss of image quality caused by both using two elements together and by combining two polarizing filters. It’s up to you to decide which route you want to go. There is a review of ND filters below, but we Like the Promaster Variable ND filter.

Extreme ND filters

Some manufacturers have produced high-quality, extreme ND filters. Typically these are rated at a 10-stop reduction, allowing prolonged shutter speeds even in relatively bright conditions.

Big 10 Stopper Extreme ND filter.

We used this filter on our last trip. It is the kind you put on the outside of your lens. We used it for one trip, but every time the rain started, our staff had to pack it up and walk to the shelter, pull it out again and reset it. It can be too much worry about. You can drop it and damage it during this in and out of the pouch time. It is an expensive item to drop, hence the worry.

Here are two shots with ND filters on for more prolonged exposure.

The ProMaster Digital HGX Variable Neutral Density Filter

It is a variable neutral density filter providing the light reduction of about 1.3 to 8.6 stops. The ND3 to ND400 density creates a darkening of the entire image, allowing you to photograph with a wider aperture or slower shutter speed than typically required.

ProMaster Digital HGX filters are the most advanced optical filters available today for digital photography featuring:

Next Generation Digital Anti-Reflection Multi Coating – Specially formulated to minimize internal reflections created by CCD and CMOS sensors in a digital SLR.
REPELLAMAX™ Element Resistant Coating – This EXCLUSIVE PROMASTER coating repels moisture, fingerprints, dust, dirt, and grime to ensure the sharpest images possible
Hardened Optical Glass – Ultra hardened optical glass resists surface scratching and stands up to the most intensive use.
Low Profile Anti-Reflective Frame – Ultra thin low profile frame helps prevent vignetting on super wide digital format lenses. The satin-like smooth finish helps to minimize reflected light.
Black Rimmed Glass – The outer rim of the filter glass is treated with a special black ink

Neutral Density Filters Explained

What is a Neutral Density Filter, and what do you use it for?

Variable neutral density filter

Extreme ND filters

The ProMaster Digital HGX Variable Neutral Density Filter

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