As a newer product in the market, variable neutral density (ND) filters have developed a divisive debate of convenience versus quality. But for photographers and videographers working in unpredictable outdoor light, or wanting to reduce their kit while on the road, variable ND filters offer a more convenient and versatile means to control the exposure of an image than a collection of fixed ND filters.
While you usually control the exposure of an image with shutter speed and aperture, ND filters offer another way to control exposure by blocking light coming into your lens before you adjust any settings. Acting like a pair of sunglasses for your lens, a fixed ND filter reduces the light intake by a set number of f-stops, and a variable ND filter creates provides a range of f-stop reductions, allowing for greater flexibility and control over your settings in unpredictable light.
“A variable ND opens up more possibilities to shoot outdoors throughout the day.”
When to Use a Variable ND
A variable ND opens up more possibilities to shoot outdoors throughout the day, by increasing or decreasing the amount of light blocked from entering your lens. With the simple twist of the front element on the filter, a variable ND gives greater and faster control of the desired exposure of your image when shooting in changing or harsh light conditions. If you’re an outdoor or landscape photographer working in unpredictable light, a videographer capturing fleeting moments or a traveller looking to lighten the load of your pack, a variable ND is a valuable addition to your kit.
Significant debate continues over the benefits of using a variable ND filter instead of a fixed ND. However, the use of any filter depends on how and where you like to shoot, as well as the quality of the lens filter.
“A variable ND offers a faster, more convenient solution to achieving the shot.”
Considering the Benefits of a Variable ND
The greatest benefit of a variable ND filter is its ability to replace a stack of fixed ND filters. It’s a compact piece of equipment that can save you heaps of room in your kit. A variable ND offers all the same benefits of a fixed ND, like giving you the ability to:
1. Use a low shutter speed for motion blur or cinematic filming effects
2. Widen your aperture for a shallow depth of field
3. Take more balanced photos in harsh lighting given the reduction in the amount of light that passes through your lens
But unlike a fixed ND which reduces light by a set amount, a variable ND offers a faster, more convenient solution to achieving the shot, because you can reduce or increase the amount of light entering your lens without having to stack or switch between filters.
“Like any decision with photography or videography gear, it’s important to consider the purpose and quality of a product before purchasing.”
Considering the Limitations of a Variable ND
As a newer product in the market, variable NDs have sparked debate about their impact on image quality with telephoto lenses and issues with vignetting with wide-angle lenses. Increasing the density of a variable ND beyond its maximum range can also create an x-pattern on the image. However, you can bypass impacts to image quality by using a slightly longer lens, or by simply framing your image while shooting, and cropping the vignetting out of your image. Similarly, using the filter in its intended range will avoid the x-pattern.
By keeping the limitations in mind, a variable ND is still a good investment if you have never used a filter and are keen to experiment shooting at different f-stops within the recommended range, or are well versed in the light conditions you plan to shoot.
How to Use a Variable ND
To begin managing light with a variable ND filter, first attach the filter to your lens. Then you can begin rotating the variable ND filter between the MIN and MAX markings on the rim, with MIN blocking the smallest amount of light from entering your lens and MAX blocking the most. Do not go past these settings, or you will see vignetting. Different variable ND filters block different ranges of light, with the widest range giving you the ability to change between ND2 (a reduction of 1 f-stop) all the way up to ND400 (between 8 and 9 f-stops). Once you have the flexibility to change light on the fly, use it to your advantage to take photos in more challenging conditions, like in harsh midday sun or a setting filled with shadows.
If you’re using a wide angle or telephoto lenses, you’d be best off using a variable ND2-32 or ND8-128 so you don’t see vignetting. And make sure you only rotate half way or until you begin to see the outer edges of your image darken. Note, vignetting won’t be an issue if you aren’t using a wide angle or telephoto lens.
“Once you have the flexibility to change light on the fly, use it to take photos in more challenging conditions, like in harsh midday sun or a setting filled with shadows.”
A fixed ND blocks a single f-stop of light exposure, and you can stack multiple fixed ND filters to achieve multiple f-stop reductions as with a variable ND filter, but the more filters your stack, the more impact it will have on image quality.
If you are shooting under consistent light conditions, like in a studio or at a set time of the day with a mostly fixed subject, fixed ND filters are a great solution. ND filters are most commonly used for slowing down shutter speeds to create motion blur – a key ingredient for creating the smoky effect in water and sky landscape shots. If you’re using a fixed ND in variable light conditions, you’ll need to keep adjusting your camera setting, or screw on different strengths of ND filters, which can be a slow and cumbersome process when capturing a quickly vanishing moment. Carrying around a stack of fixed ND filters may also present an issue if you need to minimise your kit for a trip.
Like any decision with photography or videography gear, it’s important to consider the purpose and quality of a product before purchasing. Variable and fixed ND filters present differing benefits depending on your style of photography or videography, and the conditions you’re going to shoot in. The best ND filter is as subjective as the work you create with it.