One of the secrets to the success of my landscape photography is the Neutral Density Graduated Filter—otherwise known as the ND grad. I learned about them from Bob Evans at one of his (highly recommended) workshops in Yosemite in ’05, and almost always use them in my landscapes.
A daylight sky can be several stops brighter than the foreground landscape, especially if the sun is in your frame, so if you meter the entire scene as a whole, chances are your foreground elements will be end up in silhouette. This is fine if that’s what you’re looking for, but if you’re trying to highlight your foreground features, you’ll need to open up the aperture, which will result in the sky being “blown out”, or totally white.
You can see the whole scene just fine with your eyes, because they are capable of perceiving many more stops of light than your camera. Photography is sometimes the art of compromise. In this case, you have to choose whether to sacrifice the sky or your foreground.
If you want both, there are a couple of things you can do. One tried and true technique that many photographers use (including me, when I’m in a bind) is to take two good shots, one with the landscape exposed correctly, another with the sky exposed correctly, then join them together using image editing software such as Adobe Photoshop.
There’s nothing wrong with this, but it can take a lot of time and skill if the break between the two photographs isn’t an easy, clean one, like an ocean and sky. If it’s a complex treeline, you’ll have to create a careful selection around it so you can do a better job of blending the two shots.
Enter the ND grad. These are pieces of glass or plastic, half of which is clear while the other half is tinted. The tinted side comes in different shades of darkness, or densities—typically 1, 2, or 3 stops (usually denoted as ND 0.3, 0.6 or 0.9, respectively). They come with either “hard” or “soft” divisions or lines between the two halves to accomodate your compositions. If your scene has a clean line where an ocean meets the sky, a “hard” ND Grad with the line placed right on the horizon will do the trick. If you have a mountain range or a row of trees on the horizon, a hard line would be difficult to place, in which case you might want to use one with a “soft” line.
ND Grads come in two main types. One type is circular and screws onto the end of a lens like any other filter. This is fine, but it forces the photographer to compose the photo with the line in the middle of the frame, which can make the photo look static and less interesting.
The other type is rectangular, and slides into a slot in a holder, such as the Cokin “P” series. This holder is attached to the end of the lens by means of an adapter ring. This type of filter gives the photographer more flexibility in moving that line around than with the fixed, circular one. The filter slides up and down within the holder until the line is placed correctly.
The trick is placing that line correctly, so that it doesn’t show in the final photo. You don’t want someone looking at your photo and wondering why there’s a mysterious division between light and dark in the middle of an ocean or a lawn.
Here’s how it’s typically done:
1. With your camera on a tripod and set to “Manual”, and take a shot of the scene with your light meter set to “Matrix” or “Evaluative” mode (manufacturers have different terminology) to see what it looks like. In the case of a sunset with the sun in the frame, the foreground elements will most likely be in silhouette. In other cases, depending on the intensity of the light, your sky may be blown out and look like one big “blinky” if your display is set to “Highlights” mode.
2. Set your light meter to spot metering mode and zoom in on a small area of sky. Take a reading.
3. With your light meter still set to spot metering, take a second reading of a small area in your foreground.
4. What’s the difference in the two readings? How many stops? This determines which ND Grad to use. Set your light meter back to Matrix or Evaluative mode.
5. Next, we need to decide if we should use a hard or soft ND Grad. Is your horizon a simple division between land and sky? Do you have a row of mountain peaks on the horizon? Your situation and composition will determine which one to use.
6. Compose your image again. Slide the chosen ND Grad into the holder. Now, to determine where exactly that line should go.
7. There’s a button, usually beside the lens mount, called the “depth of field preview”. When your shutter is not engaged, the aperture of your lens is wide open. Even if you’ve dialed in an aperture of f/16 or f/22, it will only take effect when the shutter is released, so you can’t really see what your chosen aperture setting looks like. This is what the depth of field preview button is for. When you press that button, you’ll notice the world suddenly go dark in your viewfinder. That’s because the aperture is now set to your chosen setting. Like being in a dark room, you need to take a few seconds to let your eyes adjust to the darkness in your viewfinder.
With the depth of field preview button held down, move the ND Grad carefully up and down until the line is where you want it to be. Remember, you’re looking for the spot where it will be the least obvious in the final photo. While you have the button pressed, take advantage of the stopped down aperture to check for any stray elements in your composition you didn’t see before. When your aperture is wide open, you can’t always see distractions that might appear when your chosen depth of field is in effect.
8. Double check to make sure your light meter is set to Matrix or Evaluative mode. Remember, you’re now “re-evaluating” the whole scene with the ND Grad in place. Set your exposure.
9. Take your picture. If all goes well, you should now have a fabulous, well balanced photograph.
You can also use an ND Grad to create effects that might otherwise be difficult or impossible, such as blurring the flow of water in the foreground during a sunset. I look forward to seeing some of the work you’ve created with ND grads. Post some links in the comments and let’s have some fun.