In the Flow

Gary Hart Photography: Autumn Drift, Bridalveil Creek, Yosemite

Autumn Drift, Bridalveil Creek, Yosemite :: Canon EOS 1DS Mark III : Canon 70-200 f/4L : 15 seconds F/16 : ISO 100

“Natural” is a moving target that shifts with perspective. Humans experience the world as a 360 degree, three-dimentional, five-sense reel that unfolds in an infinite series of connected instants that our brain seamlessly assembles as quickly as it arrives. But the camera discards 80 percent of the sensory input, limits the view to a rectangular box, and compresses all those connected instants into a single, static frame. In other words, it’s impossible for a camera to duplicate human reality—the sooner photographers get that, the sooner they can get to work on expressing the world using their camera’s very different but quite compelling reality.

Despite the creative opportunities the differences between human and photographic vision offers, many photographers expend a great deal of effort trying to force their cameras closer to human reality (HDR, focus blending, and so on)—not inherently wrong, but in so doing they miss opportunities to creatively reveal our natural world. Subtracting the distractions from the non-visual senses, controlling depth of focus, and banishing unwanted elements to the world outside the frame, a camera can distill a scene to its overlooked essentials, offering perspectives that are impossible in person.

Blurred water

Motion is one thing that an image “sees” differently from you and me. But working in a static medium doesn’t mean photographers can’t convey motion, or use motion in a scene to creative effect.

One question I’m frequently asked is, “How do I blur water?” And while there’s no magic formula, no shutter speed threshold beyond which all water blurs, blurring water isn’t that hard (as long as you use a tripod). In fact, when you photograph water in the full shade or cloudy sky conditions I prefer, it’s usually more difficult to freeze moving water than it is to blur it.

The amount of moving-water blur depends on several variables:

  • The water’s speed: Whether it’s a flowing river or crashing surf, the faster the water moves, and the greater the blur. And regardless of the speed, white water (surf or whitewater) blurs better than blue or green water.
  • The water’s direction of motion relative to your position: Water moving at right angles to your position will blur more than water moving toward or away from your position.
  • Your focal length: The longer the focal length, the greater the blur.
  • Your distance from the water: Motion blur increases as you move closer
  • And of course, the shutter speed: The longer your shutter is open, the greater the blur.

Of these variables, it’s shutter speed that gets the most attention. That’s because focal length and subject distance are compositional considerations, and we usually don’t start thinking about blurring the water until after we have our composition. To achieve a longer shutter speed without overexposing, you need to reduce the light reaching (or detected by) the sensor. There are several tools at your disposal, each with its own advantages and disadvantages:

  • Only photograph moving water in overcast or full shade.
  • Reduce your ISO (light sensitivity): Many cameras allow you to expand their ISO below their native value (usually, but not always, 100). This capability is often disabled when the camera comes out of the box, so you need to check your manual to see if your camera has a menu setting that enables “expanded ISO” (or whatever your camera manufacturer calls it). Unlike the film days, when a lower ISO (we called it ASA back then) meant better image quality, any ISO value lower than the camera’s native ISO is emulated (manipulated with internal programming) and may result in slightly lower image quality. This degradation isn’t usually enough to make a huge difference, but it’s still something to avoid unless it’s the best way to achieve a longer shutter speed.
  • Shrink the aperture (larger f-stop number): A smaller aperture reduces the light that reaches the sensor. It also increases the depth of field, which could be good, bad, or irrelevant. And a smaller aperture increases diffraction, which soften of the image. While this softening isn’t usually a problem unless you’re making big prints, its best to avoid using a smaller aperture than you need. As a general rule, I resist going with an aperture smaller than f/11 (but don’t hesitate to when it’s the only way to achieve my desired effect). 
  • Add a polarizing filter: In addition to reducing reflections, a polarizer will subtract 1 to 2 stops of light (depending on its orientation). When using a polarizer, you need to be vigilant about orienting it each time you recompose (especially if you change your camera’s horizontal/vertical orientation), and monitoring its effect on the rest of your scene.
  • Add a neutral density filter: A neutral density filter is, as its name implies, both neutral and dense. Neutral in that it doesn’t alter the color of your image; dense in that it cuts the amount of light reaching your sensor. While a dark enough ND filter might allow you to blur water on even the brightest of days, it does nothing for the other problems inherent to midday, full sunlight shooting (specifically, extreme dynamic range). ND filters come in variable and fixed-stop versions—the flexibility of variable NDs (the ability to dial the amount of light up and down) means living with the vignetting they add to my wide angle images.
  • Don’t even think about any kind of subject blur without a sturdy tripod. For help selecting the right tripod, read the Tripod Selection article in my Photo Tips section.

Other motion blur opportunities

Motion blur opportunities aren’t limited to crashing waves and rushing whitewater. For example, I love using long shutter speeds to smooth the undulations and chop on the surface of an ocean, lake, or flowing river. And a particular favorite approach of mine is blurring something floating atop moving water, like dots of foam or autumn leaves. And my favorite time and place for this is each autumn at Bridalveil Creek in Yosemite. Here, beneath Bridalveil Fall and shaded by Yosemite’s towering granite walls, are countless pools surrounded by colorful trees and fed by tumbling cascades.

The motion of the cascade’s entry and exit creates arcs and spirals of motion in the pool, punctuated by small pockets of stillness near the perimeter. Leaves fall from the trees and land on the water, or flow down from upstream, congregating on the pool’s surface. Some just make a single arced pass before continuing downstream, others join a circular dance that can last for hours. It’s usually impossible to see any organization to the pool’s motion without something floating on the surface, but a long enough exposure with leaves or floating foam will reveal a distinct flow pattern. 

After finding a pool adorned with drifting autumn leaves, I set up my tripod and camera, find a composition, and dial in a shutter speed measured in seconds. Depending on the speed of the circulation, sometimes 10-second shutter speeds are enough, but usually I try to go to 20 or 30 seconds. With the help of a neutral density filter, I’ve gone as long as 3 minutes (and maybe longer).

Once the blur patterns reveal themselves in my images, I tweak my composition and shutter speeds accordingly. Because there are usually many leaves, and each leaf takes a slightly different path depending on its size and interaction with other swirling leaves, each click results in a unique image. I’ll sometimes work a single composition for 15 or 20 minutes, collecting as many motion patterns to choose between as possible, before moving on to another composition or scene.

The image I’ve shared here is a 15-second exposure, captured at Bridalveil Creek in 2009. Because this location is always in full shade, and this was a cloudy day, the scene was dark enough that I could slow my shutter enough with just a polarizer. I’ve always felt like a polarizer is essential to remove glare from the water, leaves, and rocks in these scenes, but at the time I always had to decide between a polarizer or neutral density filter—I couldn’t do both. (I now have a Breakthrough 6-stop darkening polarizer that achieves the best of both worlds.)

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World In Motion

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