What is a ND/PL Filter?
Neutral density/polarization filters, or ND/PL filters for short, are a unique type of camera filter that combines two popular filter effects together into one single lens. In addition to having the properties of a neutral density filter, a ND/PL filter, integrates the features of a circular polarizing filter as well. A ND filter, or neutral density filter, is used to limit the amount of light that is able to reach your camera’s sensor. As a result, these filters allow you to control the exposure in your image very easily and prevent you from having to over extend the use of your camera’s settings, like ISO, aperture, or white balance. ND filters also help keep the shutter open longer on your camera, and achieve long exposure shots, the milky effect of water, and also show the movement of clouds in the sky. A CP, or circular polarizing filter, allows you to capture vividness and contrast in an image. These polarizing characteristics do not only enhance the colors of your image, but also reduce glares and reflections within your photo or video. As a result, a ND/PL filter combines the features of these two popular filter types. These filters are used to achieve smooth, flushed out photos or videos at slower shutter speeds with improved contrast and color saturation. Unlike straight ND filters that usually have a neutral color profile, ND/PL filters provide more color saturation due to the polarization effect.
Benefits of an ND/PL Filter
One of the most common questions about ND/PL filters, is why you should use them over a straight ND filter. The answer is simple actually, because instead of getting a filter that has only one set of characteristics-- the ND/PL offers you two different functions within one glass element. For example, with a ND/PL filter it prevents you from having to stack filters since it has two-in-one features. In addition, the polarizing aspect of the filter will reduce any harsh light or glare from possibly disrupting the quality of your image. This is another aspect where an ND/PL filter differs from a straight ND, as a straight ND filter does not reduce glare but rather only helps decreases the shutter speed of your camera.
Restrictions of a ND/PL Filter
Although a ND/PL filter is the best of both worlds when it comes to filter function, it does have some drawbacks that are good to know about prior to deciding to use one on location. For instance, ND/PL filters work best when shooting at a 90-degree angle to the sun because since they only remove light that’s polarized in a specific direction, they tend not to work well with wide angle lenses. This is because these types of lenses collect light in various directions; which as a result, has the ability to cause uneven light distribution in an image, such as the sky appearing darker in some areas than others making the purpose of the filter fairly obsolete.
ND/PL Filters in Cinematography
In cinematography, neutral density filters are used to control shutter speed, using the 180 degree shutter angle rule as a guide. In today’s digital terms, the 180 degree shutter angle principle corresponds to a shutter speed to frame rate ratio of 2:1. To achieve smooth video with natural looking motion blur, cinematographers use ND filters to achieve this 2:1 ratio. In environments where there is too much harsh light from extreme glare or haze, ND/PL filters can be used as a direct replacement for ND filters to reduce shutter speed and also polarize the scene.
How Many Stops is an ND/PL?
Common strengths of ND/PL filters include ND4/PL, ND8/PL, ND16/PL, ND32/PL and ND64/PL. Unlike normal ND filters that strive to have a neutral color profile, ND/PL filters provide more color saturation due to the polarization aspect. For example, a ND4/PL reduces shutter speed by 2 stops while increasing color saturation, while the larger stop ND64/PL reduces shutter speed by 5 stops while also improving contrast and increasing color saturation. The ND4/PL is suitable for sunrise, sunset or similar low light conditions, while the ND64/PL is reserved for shooting at 24p in extreme light.
Do I Need an ND/PL Filter?
Aerial cinematographers as well as GoPro users shooting at the beach or in other bright and reflective scenes often use these hybrid ND/PL filters instead of regular polarizing or neutral density filters to get the benefits of both ND and PL filters in one lens element. ND/PL filters are also being utilized with full frame, production grade digital cameras, with companies like PolarPro setting the bar with the recent release of the QuartzLine, which features a few different ND/PL options for full frame DSLR and mirrorless shooters.
Shooting through one ND/PL lens element, especially with a drone camera that is prone to camera shake and atmospheric noise, will produce better results than stacking polarizing and ND filters to achieve the same benefits. ND/PL filters also add less weight to a camera gimbal than stacking filters. And after all, the idea of a camera filter is to help enhance your image, not to introduce noise or damage your expensive equipment.
If you’re looking for some ND/PL filters for your DJI drone, GoPro or full frame DSLR/mirrorless camera, be sure to check out PolarPro’s full production-grade filter line.
Edited by Carly San Filippo
Written by Scott Fairfax