The Magic of Long Exposures
I still remember some of the images that made me want to learn photography. Many of them involved long exposures. They were often taken at dawn or dusk. Those hours typically offer softer and more colorful light than we see when the sun is up. Long exposures during those hours blur unnecessary details in a way that yields a simpler and, to me, more satisfying image.
Editor's Note: This is a guest blog post from Don Peters
The opening shot was taken at twilight from the balcony of a condo in central Phoenix. The vivid colors result primarily from the mixture of natural and artificial light. We usually see such a mixture only at dawn and dusk. The image was exposed for thirty seconds at f/13. The long exposure time caused moving things to blur. The clouds have soft edges because they moved during the exposure.
The edges of shadows in the foreground also moved enough in thirty seconds to soften them slightly. It took me a long time to figure out why long exposure times produce a general softening effect in photographs. Even in the lowest light, there are always shadows. The boundaries between bright and dark areas are always moving. In as little as half a minute, some areas that were illuminated will become shadowed, and some that were shadowed will become bright. A long exposure averages the brightness in such areas and produces soft edges between areas of different luminosity. At least, I think so. I’m often wrong.
There’s nothing difficult about taking long exposures. A tripod is essential, unless you want motion blur for creative reasons. We ought to be using a tripod anyway—in the kinds of photography that permit doing so—for any number of reasons. It’s highly advisable to use a cable release.
I typically shoot in Aperture Priority and use Automatic Metering because of the changing light level. If you set the exposure manually, you’ll need to adjust it often. Automatic Metering, by contrast, will adjust to the changes in the light. Automatic Metering will produce a shot that looks like midday, unless you use the Exposure-Compensation feature. In a twilight scene such as the opening shot, I usually set the exposure about a stop-and-a-quarter below what the meter suggests, take a test shot, and make further adjustments as may be needed.
With most cameras, the meter will not tell you how long an exposure ought to be, if the answer is longer than thirty seconds. The solution is to increase the ISO until the meter suggests an exposure of less than thirty seconds, and then do the math required to figure out the correct exposure time. If an exposure of twenty seconds is appropriate at ISO 400, for example, the camera will need four times as long to expose at ISO 100, or eighty seconds. For such an exposure, you’ll need to use the Bulb setting, and time the exposure with a watch.
A common problem when shooting landscapes at dawn or dusk is that the sky can be much brighter than the ground, and brighter even than a body of water that reflects the sky. That was the case when I took this photograph of a lake in Arizona’s White Mountains. The best solution is to use a graduated neutral-density filter to darken the sky. In this instance, I used a three-stop filter. You can, instead, bracket the exposures and combine them. The results of that approach, however, never ring as true to me as an image in which a graduated neutral-density filter was used.
Before you take a long exposure, consider what’s moving in the frame—and will therefore be blurred as a result. To me, the look of blurred clouds and water is usually appealing. The look of blurred foliage usually isn’t.
Long exposures are my favorite way to photograph moving water. There’s no truly accurate way for a still camera to photograph moving water. A fast exposure that freezes water droplets in mid air doesn’t capture what our eyes see. Neither does a long exposure that turns the water into a milky blur. Blurred water, though, comes closer to what I experience when looking at moving water, so it’s almost always my choice.
If we shoot in sufficiently low light, we’ll have no choice but to use an exposure that is long enough to blur the water. In brighter light, however, we may need to do what we can to slow the exposure down so as to induce blur. That includes using the lowest possible ISO, a small aperture—and sometimes, a polarizing filter.
When those won’t suffice, we can slow the exposure way down with a very dark neutral-density filter, which I think of as dark glass. Mine is a nine-stop Hoya. It increases the exposure 400 times. On a recent shoot, I arrived at a stream later than I had planned. There were already patches of sunlight in the stream. I couldn’t get a slow enough exposure to blur the water without using the dark glass. Here is a test shot of a stream taken without the dark glass, and a shot taken with the dark glass:
You can probably see why I wanted to use the filter. I processed the second one more carefully than the first, since the first shot was nothing I’d ever want to keep. The primary difference between the two images, though, is the exposure time. The first image was exposed for a tenth of a second; the second image was exposed for fifteen seconds. Using dark glass filters can be somewhat tedious, but that’s a subject for another day.
Some photographers, such as Chris Friel, have used long exposure times with handheld shots to produce motion blur for creative reasons. I think Friel is one of the most interesting photographers working at the moment. I seldom shoot slow, handheld shots as he does, but I did use the dark glass filter to take a handheld shot as I was driving home from work one day. The exposure took six seconds. I won’t explain exactly how the shot was taken because the explanation might tend to incriminate me.
Most viewers will accept a lot of blur in an image, as long as part of the image is sharp. When the entire image is blurred, as is the case here, viewer resistance increases sharply. The result here, though, is much more interesting and evocative to me than a sharp photograph would have been. Besides, if we stay safely in the middle of the road, we’ll never do anything very interesting.
The best way to learn to use long exposure times is to use them, make mistakes, and learn from the mistakes. Isn’t that the best way to learn almost every aspect of photography?
Don Peters’ photographs can be seen at http://cornflakeaz.smugmug.com/