Equipment

Using ND Filters to Balance Ambient Light With Artificial Light

Published July 24, 2015

A week or so ago, I posted an article about some of the features on the Profoto B1 that separate it from the competition. Among those features, was High-Speed Sync, allowing you to use off camera lighting at shutter speeds faster than 1/200th of a second. Today, I would like to tell you about how to achieve that same goal, but with the use of one of my favorite tools – The Neutral Density Filter.

What is a Neutral Density Filter?

Typically, I’ve found the best way to describe a Neutral Density filter to photographers, is calling it a pair of sunglasses for your camera. It doesn’t add any color gradients to your images (or a good one won’t at least), but simply, just stops the amount of light coming into your camera lens. This can be effective for a lot of reasons. Landscape photographers often use them to create interesting effects using a long exposure. An ND filter allows you to stop down your shutter speed, and get super smooth water and clouds in images when extending the time the shutter is open. But the opposite is also true, and ND filter can allow you to open your aperture more, allowing for a shallow depth of field in your portrait work when lighting on location. This is how I often use ND filters for my work, and then compliment the subject with flattering light coming from off-camera flash.

Mastering the ND Filter Technique

Many people often ask me why I use ND filters in my work, and the answer I always give them is balance. When I began shooting outdoor portraits, I was frustrated that my skies were always white in color, instead of showing the great depth of blue that I often see. In order to fix that, I needed to find a way to balance the ambient light with flash, and began using an Alien Bee B800 with my work, however, this brought a whole new realm of problems for me. For one, in order to get the colors out of the sky, I often had to shoot at f/11+, cause my shutter speed was limited to 1/200th of a second (The max sync speed for most traditional strobes & flashes). The result was an image with everything in focus, and with no draw to the subject in the photo. So I went back to the drawing board.

Image Taken Using a 4-Stop ND Filter to balance Ambient and Artificial Light

ND Filter Allows me to Balance Lights on Location, Giving me a Shallow DOF

I began using ND filters with my work. A 5 stop ND filter, would allow me to open up my aperture 5 whole stops (f/11 to f/2), giving me a nice shallow depth of field, that brought focus to the subject in my image, while maintaining all the colors from the scene. 5 stops would turn an image at f/11, 1/200th of a second and at ISO 100 into an image shot at f/2, 1/200th of a second and ISO 100. The end result is a more flattering image, with focus brought to your subject.

Types of ND Filters

Generally speaking, there are two types of ND filters I’ve used in the field – the standard ND filter, and the Variable ND filter. The standard ND filter is a single piece of glass that has a specific number of stops of light. These are nothing more than a darkened piece of glass, that allows less light into the camera, so you can open up your aperture or shutter speed as needed. The next type is much more interesting – the Variable ND filter. The Variable ND filter allows you turn the dial on the filter, giving you a broad range of stops, depending on how much you turn the dial. These Variable ND filters typical range from 2-stops to 9-stops of light, allowing you full adjustments in between that range.

Which is Best For You?

Traditionally, I recommend the Variable ND filter over the Standard ND filters. While variables cost much more (up to $500 in price), they allow for far more versatility in your work, and without the need to change filters while on location. In addition to that, stacking filters will often give you a loss in image quality exponentially, so I prefer to keep as few piece of glass in front of my lens as possible (and the highest quality of glass).

At LensRentals, we have a huge array of ND filters for people to rent. So if you’d like to give this technique a try on your own, be sure to look through our inventory of ND filters for your next shoot. When done correctly, you can add more interest to your images using depth of field, bringing the attention exactly where you’d like it.

Author: Zach Sutton

I’m Zach and I’m the editor and a frequent writer here at Lensrentals.com. I’m also a commercial beauty photographer in Los Angeles, CA, and offer educational workshops on photography and lighting all over North America.

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Tuco

Zach, good article. I use 3 and 5 stop NDs for the more simple purpose of shooting wide open (for subject isolation) on bright days. Blasting fill makes a lot of sense. In that light, there is no problem seeing through 3-5 stops to compose. The ‘welding shield’ NDs are the ones that are a pain to use.
Zach Sutton

@Frank – Perhaps I should have specified more. Balance in the sense of being able to shoot at a shallow depth of field while using off camera flash.

If you’ve shot using lights before, during a somewhat sunny day, you’ll notice in order to make it so the light makes any difference on your subject, you need to shoot at a very high power, and at f/11 or so, to get the correct exposure on the ambient light (since your shutter speed is limited to 1/200th). In order to make use of a lenses quality wide open (or even getting the sharpness by only stopping it down about 2 stops or so), you need something to prevent so much ambient light from coming into your camera lens. This can be done a variety of ways (Lowering your ISO, fo example), but the ND filter allows you to effectively stop down all the light coming into your camera, so you can use lights on location, getting the colors from the background, and maintaining a shallow depth of field. The easiest way (besides using high-speed sync) is to use an ND filter to alter the amount of light hitting your sensor.

@Richard – Yes, you’ll need more flash power, but you might find that you don’t need that much more. If you bring the light in close, you can make use of the inverse square law, and maintain nice soft light, while not using too much power. I’m often able to shoot on location with a 300Ws and only have it at about 1/2 power with ND filters attached to my lens.

@chris – You’re absolutely right. It was an oversite, and I’ll edit the article to be more clear, thanks.
Frank Kolwicz

I’ve read the article twice, now, and still don’t get the “balance” part. The filter is over the lens, so all the light, whether from flash or ambient is equally decreased for any given flash setting and, if you need a lot of light to fill against full sun, you may well run out of flash power. Yes, you will have to open the aperture to compensate, if you’re already at the max synch speed or you could use proportionately longer shutter speeds for motion effects, as you say. Where’s the balance in that? I take balance in this context to mean between the flash and ambient and putting the ND filter on the flash might do that in some instances, but that’s not what you describe.

As to the badly conceived jargon: “stop down your shutter speed” and “stop down my aperture 5 whole stops”. I suggest that you adopt the standard photographic terminology. What you describe regarding shutter speed is simply “use a slower shutter speed” and what you call stopping down the aperture is actually “opening the aperture”.
Richard

How does it balance the flash? Granted it brings the f-number down which is really nice. I find it frustrating when my camera demands f/11 because of its sync speed limitations. (And think of my friend with his leaf shutter).

But doesn’t the ND filter also filter the flash light? So you still need plenty of flash power to compete against the sun. You just get to use a wider aperture for depth of field purposes.
chris foster

Zach, This is a mostly useful article, but “stopping down” your aperture 5 stops to give a shallow depth of field, is incorrect, and should say “opened up”. Also the term “stopping down” is not used where shutter speeds are concerned, especially when you are trying to explain that a slower speed will allow intentional blurring of parts of the scene. You are trying to describe a longer exposure, not a shorter one!
finnan haddie

ND filters causing dark viewscreens are typically not a problem with mirrorless cams 😉

however, vari NDs are just two stacked polarizers, not exactly a good thing, neither to reduce flares, nor to get an evenly colored sky with wide angle lenses

also, some sensors are prone to high levels of infrared, which are not blocked by standard ND and vari ND filters, resulting in a color cast when using high density ND (say 4 stops or more)
look for “hot mirror” or “IRND”
Lynn Allan

Helpful article. Thanks.

The use of the word “balance” at first suggested “white balance” when there are difference sources of light temperature. Perhaps the word “equalize” would be clearer?

HSS … possibly High Speed Sync? Or not?

There is another kind of ND filter … GND … graduated neutral density.

I don’t own one nor have used one, but my understanding is that they are typically clear or semi-clear at one extreme, and quite dark (two stops or more) at the other extreme. There may be a gradual transition, or a rather abrupt transition.

I think the GND’s are typically used for high contrast landscapes that include dark’ish foreground and bright sky. Their use can avoid the use of HDR.

I think a polarizer can be used as a ND filter, with the orientation of the two glass pieces to selected to darken the image.
starship

HSS?
Cody

Great article, what Ed says is true but usually on 6+ stops on ND. I’ve used ND 3-5 and can still get what i need. I’m on EVF now too with Sony.
ed okie

Your story fails to address a major downside of ND filters… the viewscreen grows dark, sometimes “invisible” because of darkness. Composition, focus, etc often becomes exceedingly difficult, sometimes impossible. ND’s are not a silver bullet, an aid in one aspect, but hindrance in many other areas.