A few months ago, wedding photographer and Fstoppers writer, Trevor Dayley made a post about his favorite thing in his camera bag. Spoiler - it was a tilt shift lens, and the work he was able to produce with it made for some interesting and beautiful wedding and engagement photos. However, Trevor and I shoot entirely different styles, so what's my favorite thing in my camera bag?

It's simply, the Neutral Density filter. Being a strobist and commercial photographer, it is the one thing that I use on every single one of my photo shoots. I literally have 6 of them sitting in my camera bag right now, used primarily as backups if nothing else. So what is an ND filter and how do I use them?

What is a Neutral Density Filter?

As a portrait photographer, the best way I can describe a neutral density filter as is a pair of sunglasses for your lens. In other words, it blocks light from entering your lens, and the amount of blockage depends on the stop rating of the ND filter. A (good) ND filter won't provide any color shift to your photos, do any fancy tricks on its own, or alter your photos in camera.

So why would you want to block light from coming into your lens? Simple, for the same reason you want to shoot at ISO 100 and not ISO 400 on a bright sunny day. By reducing the amount of light that enters your camera, you're able to slow your shutter down and/or open your aperture wider for the shots. This becomes particularly handy when using off camera lighting, as it allows you to maintain the 1/200th of a second shutter, while opening up your aperture to get a shallower depth of field.

So in layman's terms, if I'm using an ND filter that is 5 Stops, that allows me to drop my shutter or aperture five stops total. So if I was shooting a session outdoors on a bright sunny day using the settings 1/200sec and f/11 (To expose the background correctly), with a 5 stop ND filter, I'd now be sitting at 1/200sec and f/2.0.

Why Do I Do This?

The biggest reason is balance. You'll often find that if shooting natural light on a clear sunny day, you're going to be left with white, or near white skies. This is simply because the sky is overexposed, and has lost all detail in it as a result. When firing with strobes, if you want to exposure the sky, you'll have to "beat the sun" in terms of strobe power, leaving you with an image that is exposed, but at a high f-stop, pushing everything in focus, and losing interesting focal planes. An ND Filter will let you expose the background completely, while allowing you to use your strobes to correctly expose the foreground, all while being able to select your aperture (since your shutter speed will be maxed out at 1/200 a sec). By using ND Filters, suddenly my super sharp f/11 image with everything in focus has a nice bokeh at f/2 to compliment the image and give it a more professional look.

Types of ND Filters

Generally speaking, there are three types of ND filters. The first, is the standard ND filter. These filters provide a specific stoppage of light, and that cannot be altered whatsoever. These will have a variety of filter sizes and stop numbers, and will be of much higher quality than the other option, which is Variable ND filters.

What a variable ND filter is, is a ND filter that covers multiple stoppage levels depending on how much you turn the filter's dial. They typically vary from 2-stops of light, to 9-stops. Because of how these work, the quality of them is reduced, and a strange purple or green vignette can come from them when shooting at higher filter stops. However, these filters still work great for everyday use, and provide excellent image quality if they're a higher quality brand. Because of the versatility of these types, they do typically cost a bit more than your standard ND filter.

The third is the ND filter (in my opinion) built specifically for landscape photographers, which is the gradient ND filter. Much like the name suggest, the Gradient ND filter will only provide a stoppage of light for a portion of the filter, gradually increasing stops as it gets closer to the edge. This is useful when trying to match the exposure of the sky with the exposure of the foreground, and particularly helpful with landscape photography during sunny days.

So Which One Do I Prefer?

I am a believer in the Variable ND Filter personally. Despite reducing the image quality and creating fringing caused by the filter, I still find the problems to be minimal, especially when using a higher brand filter. I also often manual focus, meaning that I'm still able to create incredibly sharp images, assuming my eyes are working right.

Currently, a cameras downfall is the inability to work with off camera lighting beyond 1/200th of a second (with the exception of hyper syncing). With lower ISO speeds (ISO 50 for example) modern cameras are often able to counteract that issue, but most times, it's not nearly enough. So if you want to be a lighting snob, and still get that great shallow depth of field, ND Filters are a must for shooting in bright conditions.

The current brand of Vari-ND filter I use is the Fader II, by Light Craft Workshop. I bought it for its price point, and quality that it does produce. When stacking ND filters, I have noticed some strange color toning coming from it, but for its normal use, it works wonderfully and works exactly how I'd need it to. This strange color toning is known as 'X Factor' and will occur on all Variable ND filters at one point or another, especially when staking them to achieve 12+ stops (like I was doing).

The Top Brands of ND Filters

For normal ND Filters, Lee, B&W and Hoya are all considered the Mercedes-Benz of filters. They're pricey, especially given that they're nothing more than a tinted piece of glass, but they have some of the highest quality available for ND Filters (Often filters on your camera will soften your images slightly). For Variable ND Filters, there is far more varying opinions. Here is a list I have built based on personal experiences and reviews that I've researched on the internet.

Also, be sure to check out Jaron's review of the Fotodiox Wonderpana - a ND system for Wide Angle Lenses.