The Benefits of Using Neutral Density (ND) Filters & Gels in Video Production [ReelRebel #29]

In a previous ReelRebel episode on video lighting tips we taught you how you can utilize gels on your lights in order to keep your color temperature correct to get the best look for your shot.  In this episode Stephen gives an overview of neutral density (ND) filters and gels for video - which are kinda like sunglasses for your DSLR camera or lighting rig and can help you better manage exposure in various lighting conditions.

The same way you need to ensure your color temperature is right to minimize color correction in post-production, you also need to make sure the lighting of your scene or parts of your scene are exposed correctly and not too bright.  One way to compensate for lighting that's too bright is to use a ND gels and/or filters.

Neutral Density (ND) Filters and Gels for Video

Before I go into any of this, the truth is that no gel or filter can substitute for shooting at the right place and time to capture the most appropriate lighting.  However, properly used, filters and gels can allow the the videographer to capture a scene that may be impossible to capture otherwise.

Lighting Neutral Density Gels

Most lighting gels are used for controlling color temperature - however, neutral density gels can be used to help change and control the intensity of the light.

Neutral density gels are most commonly available in grades:

• ND3 (0.3) - takes away 1 stop of light = -1 F-Stop
• ND6 (0.6) - takes away 2 stops of light = -2 F-Stop
• ND9 (0.9) - takes away 3 stops of light = -3 F-Stop

Essentially, the higher the number the darker the gel will be which in turn will cut back on the intensity of the light.

As an example, if you have a particular lamp that's putting out too much light relative to other lights, you can slap a ND gel on that light to even out your lighting set.  Or, if you are shooting inside and too much light is coming through the window, you can put a neutral density gel on the window to cut down the intensity coming from that bright sunlight.

ND Filters for Video

While ND gels can be used on lights to control the intensity of a given light source, you can use ND filters on your camera itself to change the intensity (lessen) of the entire scene.  For the most part, neutral density filters for DLSR camera lenses come in the same intensities as the gels, although there are other grades if you find you need them.

One of the things that determines your depth of field is your aperture and F-stop.  When you close your aperture to bring down the brightness you start to deepen your depth of field and at the same time lose a lot of the artistic look that a shallow depth of field can provide.  By placing an ND filer on your lens, you can maintain the shallow depth of field you may want for your shot by keeping your aperture open but not over-exposing the shot..

Graduated Neutral-Density Filters (Grads)

There are also graduated neutral density filters, aslo known as split neutral density filters, that will add a brightness and intensity on one side of the shot while tapering it off on the other.   In general, if the scene that you're shooting has a contrast range that exceeds the dynamic range of your DSLR camera, then use of ND filters is a must. However, there are many times where you would choose to use them even when this is not the case.

Graduated ND filters really only work when there's a lineral transition between light and dark areas in the image.  So, a good example of a use case would be a shot at the horizon whereby the sky is too bright when compared to the foreground.

Picture demonstrating the effect of a graduated neutral-density filter

You can purchase 1-stop, 2-stop, 3-stop graduated ND filters all the way up to a 5-stop filter.

Using the appropriate filters and gels can ensure a better looking video and as mentioned, limit your editing time in post-production.

QUESTION: What filters and gels do you use most often when shooting video?