One of the things that helps a photographer elevate his or her photos, is the ability to manipulate the light available in a scene to produce a photograph that transforms the scene in a predictable way. When I first began photographing 30 years ago, it was all I could do to make sure my exposure was correct - not too light, not too dark, and the things that I wanted to be in focus, were in focus. As I grew as a photographer, I began to better understand how I could manipulate my settings- aperture, which is the opening in the lens that allows light into the camera, shutter speed, which determines how long that light enters the camera, and ISO, which determines how sensitive the camera is to that light.
A quick little Photo 101 lesson for the uninitiated. I promise I will keep this non-technical, but to understand how I create my images, you have to know some very basic things. In addition to determining the amount of light, aperture also determines how much of your scene is in focus from foreground to background. For instance, in sports photos, if you look, the background is often blurry. While in my landscape photos, everything tends to be sharp. This is known as depth of field. To make everything sharp, I need to set my aperture to a small opening, which limits the amount of light entering the camera. Shutter speed, in addition to determining how long light enters the camera for, also determines the way movement looks in my scene. Ever take a photo of someone with a camera or cell phone, and they were moving and came out blurry? That's a slow shutter speed, too slow to stop the motion of the person in the shot. In contrast, a fast shutter speed is used in sports photography much of the time to freeze the action. Finally, ISO, for me, is a setting that floats. I set my aperture and shutter according to the look I want, and shutter according to the way I want movement to look in my photo. Then I adjust my ISO to whatever it needs to be to make the photograph the proper exposure.
But sometimes, there's more light than I need to make the movement look the way I want. If you look at my seascape images, for instance, you can see that I often don't freeze the water. It often looks painted in. If there's too much light, I can't get that look unless I find a way to reduce the amount of light. This is where filters come in.
Filters are simply pieces of glass or optical resin that mount in front of your lens and manipulate the light. For the past few years, I've partnered with Lee Filters and have used their filters for just about every photo I've taken since. The first filter in my camera bag is always a circular polarizer. In simple terms, a polarizer cuts down haze and reflected light, making the image clearer. Many people refer to it as "the blue sky filter" because it reduces the amount of scattered light in the atmosphere, allowing the camera to capture the true blue of the sky. You may have noticed the effect yourself when you wear a pair of sunglasses, as those are polarized as well.
"Fogbow" is a perfect example of polarizer use. That morning in Lubec Harbor, there was a layer of fog enveloping the lobster boats. You can see above, the vibrant blue sky, and a very clear and distinct fogbow arcing over the lobster boats. The image to the left, taken several minutes earlier (notice that a couple of boats pulled out between shots), I didn't use a polarizer. The fogbow is less distinct and the sky is less vibrant. The polarizer reduces haze throughout the scene. My finished image does have a touch of contrast added as well, but there's a reason I edited that photograph instead of the one at left, and that is that it's simply clearer because I thought to add the polarizer to my lens.
For photographs with lots of foliage, whether it be green or colorful autumn foliage, polarizers can help that color just pop. Light tends to reflect off of the leaves on trees, which ends up sapping the vibrance of the colors. Adding a polarizer to my lens, and adjusting the filter until I get a look I like. The polarizer really made my photo of Maroon Bells perfect, and below, it made the green on Tumbledown Mountain, as well as the sky, absolutely vibrant.
Neutral Density Filters
Neutral density filters are simpler than polarizers. All they are is dark pieces of glass that reduce the amount of light entering the lens. Think of it as window tinting for your camera! The filters come in different densities, or shades, so you can use just the right amount. These filters are what I use when I want a slower shutter speed, but using such a slow shutter speed would mean the photo would be overexposed because there is too much light. In the image below, "Sunrise on South Beach", I did not use a neutral density filter. You can see that the movement of the water is fairly frozen and thus the water is sharp.
In "The Low Country", below, I wanted to show the movement of the water around these stumps on the boneyard beach in South Carolina. At one time, these stumps were mighty oaks before the Atlantic Ocean encroached on them and eventually wore them down. I tend to have a pretty good idea what shutter speed I want, knowing how each shutter speed will render the motion of the water. Neutral density filters (also called ND filters) are rated in stops, so I know how dense each one is. In this case, I didn't need a very dark filter, just enough to slow my shutter speed down to get the motion I wanted. For the photographers out there, I'll normally use a 3-stop neutral density filter as my lightest one.
I did something similar below with "December Sunrise in Ogunquit". I wanted to slow down the shutter just enough to get that water movement around the rocks. With the sun rising, the light was getting brighter rapidly, so adding the neutral density filter was essential to get the effect I wanted.
With bigger waves the effect can be even more pronounced, as in "Morning Glow on Bailey Island" below. The big waves crashing against the rocks were impressive, but I wanted a more expressive photograph than freezing the splash would have gotten me. Using a 3-stop neutral density filter enabled me to slow the shutter speed down enough to give the wave a painterly feel, while still maintaining the overall shape of the wave. In images like this one, if you use too slow a shutter speed, the shape of the moving object, in this case, the wave, can be lost completely, as we'll see below when I talk about even longer exposures.
Even Longer Exposures
So even though I'm using slower shutter speeds, by using more extreme slow shutter speeds I can create some really cool effects. As I mentioned, a 3-stop neutral density filter is fairly mild in terms of how dark it is. Sometimes, if the conditions are right, I will use a 10-stop neutral density filter to get a REALLY slow shutter speed. To give you an idea, the human eye can't really see through a 10-stop ND filter. It's just black glass. When I say slow shutter speed, I mean two minutes or more. This means anything moving quickly will likely not even register in the photograph, so people passing through the shot, or cars, will be invisible, unless they stop for a few seconds. Waves on water won't register at all, so water takes on a flat look, like ice, or glass.
"Spring Point Ledge Light Station", above, is a great example of what can happen when using an extreme slow shutter speed. This exposure was four minutes long, allowing clouds to move through the scene over the lighthouse, and allowing the waters of Portland Harbor to render as smooth as glass. That morning was pretty gray, with flat light, and thus, the scene was kind of uninteresting. But adding the 10-stop neutral density filter allowed me to take a scene that was kind of drab, and create an interesting photograph.
Graduated Neutral Density Filters
Graduated neutral density filters are used to help balance a scene with two areas of differing brightness. As you can see on the left, half of the filter is dark, while the other half is clear, and there is a gradual transition between the two areas. There are soft, medium, and hard transitions, and even reverse grads, where the middle is darkest, depending on the scene and the look you're going for. I find the soft grads tend to be most useful, as they tend not to be obvious. Hard grads and reverse graduated neutral density filters can be easy to spot at times, especially if their placement isn't just right.
These filters are useful when the sky is brighter than the foreground, such as at sunrise or sunset, but can be used in other ways as well, so it's best to keep an open mind for situations where their helpfulness might not be obvious. In "Cypress Symmetry" above, I used a 3-stop soft edge graduated neutral density filter to help keep the sky from being much brighter than the water.
"Daybreak" above, is an example where I was able to use a reverse graduated neutral density filter. With the sun just below the horizon, the brightest spot was right in the middle of the scene, so I placed the middle of the reverse grad on the horizon, to darken that area, and then the density fades as it goes up in the image. The result is that I was able to show more detail in the foreground rocks, which are dark to begin with, because the sky was now not as bright as it would be without the filter.
I made similar use of a reverse graduated neutral density filter for "Clearing Storm in the Badlands" above. The setting sun against the foreground ridges was especially high contrast. Without the filter, I would either lose detail in the sky, assuming I properly exposed the foreground, or the ridges in the foreground would have been too dark if I had properly exposed the sky. Using a reverse graduated neutral density filter allowed me to properly expose for both.
You might have noticed, but basically, if anything crosses the horizon line between the foreground and background, I use a soft-edge graduated neutral density filter, because the transition is so gradual that it isn't seen. If I use a hard edge or a reverse grad on a shot like "Day's End at the Schoolhouse", you'd see the hard line across the school building. If I have a clear horizon with nothing crossing it, I can use a hard edge or reverse grad.
That's my use of filters in a nutshell, in the simplest way I can explain. There are other ways to achieve similar results for most of these, especially for the graduated neutral density filters. Because the grads only affect a portion of the image, some photographers will take two images of different exposures and blend them together. On occasion I do that as well, but the issue with that approach is that if anything changes between exposures, if the camera moves slightly, or if something in the scene moves, it can be more difficult to blend. I prefer to get it in one shot if at all possible, as there's less that can go wrong.
I believe my approach works well for me, given that there are very few photos in my galleries that weren't taken with some sort of filter. But every photographer has to choose a way of working that suits them best.