Eloquent Images by Gary Hart
Insight, information, and inspiration for the inquisitive nature photographer
Motion
Autumn Swirl, Half Dome, Yosemite
True story
I once had a photographer tell me that he didn’t like blurred water images because they’re “not natural.” The conversation continued something like this:
Me: “So how would you photograph that waterfall?”
Misguided Photographer: “I’d use a fast shutter speed to freeze the water.”
Me: “And you think that’s more natural than blurred water?”
Misguided Photographer: “Of course.”
Me: “And how many times have you seen water droplets frozen in midair?”
Misguided Photographer: “Uhhh….”
Photographic reality
The truth is, “natural” is a target that shifts with perspective. Humans experience the world as a 360 degree, three-dimentional, multi-sensory reel that unfolds in an infinite series of connected instants that our brain seamlessly processes as quickly as it comes in. But the camera discards 80 percent of the sensory input, limits the view to a rectangular box, flattens an entire dimension, and compresses those continual 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 in their hands (or more specifically, atop their tripod), many photographers expend a great deal of effort trying to force their cameras closer to human reality (HDR, focus blending, and so on)—while not inherently wrong, that approach misses opportunities to reveal overlooked aspects of our complex natural world. Eliminating the distractions of 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.
Motion
One of the most obvious, and powerful, differences between the camera’s and our own view of the world is motion. Though a still image can’t display actual motion, it can convey the illusion of motion that, among other things, stimulates the viewer’s into imagining the motion—and we can control. While nothing like our experience of the world, a camera can freeze the extreme chaos of a single instant, or combine a series of instants into a blur that conveys patterns in the motion indistinguishable to the eye.
Combining creative vision and technical skill, a photographer chooses where on the continuum that connects these extremes of motion will fall: The instantaneous drama of a crashing wave, or the soothing calm of soft surf; the explosive power of a plunging river, or the silky curves of flowing cascades. Or perhaps someplace in the midrange of the motion continuum, stopping the action enough that discrete elements stand out, but not so much that the sense of flow is lost.
Blurred water
One question I’m quite frequently asked is, “What shutter speed do I use to 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 photographing 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 (which is why I have very few images of water drops suspended in midair).
In addition to freezing motion or revealing a pattern of motion, an often overlooked opportunity is the smoothing effect a long exposure has on choppy water. I photograph at a lot of locations known for their reflections, but sometimes I arrive to find a wind has stirred the water into a disorganized, reflection-thwarting frenzy. In these situations a long exposure can smooth the chop, allowing a gauzy version of the reflection to come through. Rather than the mirror reflection I came for, I get a pleasing ethereal haze that captures the reflection’s color and shape.
The degree of water motion blur depends on several variables:
- Shutter speed: the longer your shutter is open, the greater the blur
- The water’s speed: the faster the water, and (especially) the more whitewater (green water, no matter how fast it’s moving, doesn’t usually display a lot of motion blur), the greater the blur
- Focal length: the longer the focal length, the greater the blur
- Distance from the water: the closer the water, the greater the blur
- The angle of view: You’ll get more blur photographing water at right angles to the direction of motion than you will with water moving toward or away from you
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.
You have several tools at your disposal for reducing the light reaching your sensor (and thereby lengthening your shutter speed), each with its advantages and disadvantages:
- Don’t even think about any kind of blur without a sturdy tripod. For help selecting the right tripod, read the Tripod Selection article in my Photo Tips section.
- Reducing ISO: Since you’re probably already at your camera’s native ISO (usually, but not always, ISO 100), this option often isn’t available. Many cameras allow you to expand the ISO below the native value, usually down to ISO 50. That extra stop of shutter duration you gain might come with a (very) slight decrease in image quality—most obvious to me as about 1/3 stop of dynamic range lost.
- Shrinking your aperture (larger f-stop number): A smaller aperture also buys you more depth of field, but it also increases diffraction. And lenses tend to be less sharp at their most extreme apertures, so as a general rule, I resist going with an aperture smaller than f/11 unless it’s necessary. That said, I often find myself shooting at f/16 (and sometimes smaller), but it’s always a conscious choice after eliminating all other options for reducing light (or it’s a mistake, something pros aren’t immune to).
- Adding 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 when you change your camera’s horizontal/vertical orientation), and monitoring its effect on the rest of your scene.
- Adding 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. 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 wide angle images. (I use Breakthrough Filters.)
Before Sunrise, South Tufa, Mono Lake
Here a 3-second exposure smoothed a wind-induced chop and restored the reflection.
Because blurring water depends so much on the amount of light reaching your sensor, I can’t emphasize too much the importance of actually understanding metering and exposure, and how to manage the zero-sum relationship between shutter speed, aperture (f-stop), and ISO.
Read my Exposure basics Photo Tips article
Bracketing for motion
Back in the film days, we used to bracket (multiple clicks of the same scene with minor adjustments) for exposure to increase our margin of error. But in today’s world of improved dynamic range and pre- and post-capture histograms, exposure bracketing is (or at least should be) limited to photographers who blend multiple exposures. Today I only bracket for scene changes that will give me a variety of images to choose between later.
Often my scene bracketing is for depth of field, as I run a series of clicks with a range of f-stops, then decide later whether I want a little or a lot of DOF. But my most frequent use of scene bracketing is to capture a variety of water motion effects. I start by finding a composition I like, then adjust my shutter speed (compensating for the exposure change with ISO and/or f-stop changes) to get different motion blur.
River and stream whitewater is usually (but not always) fairly constant, so my adjustments are usually just to vary the amount of motion blur. But when I’m photographing waves, the timing of the shutter click is as important as the motion blur. It helps to stand back and observe the waves for a while to get a sense for any patterns. Watching the direction of the waves and the size of the approaching swells not only allows me to time my exposures more efficiently, it also keeps me safe (and dry).
Star motion
Few images validate the power of the camera’s unique vision better than a scene etched with the parallel arcs of rotating stars (yes, I know it’s not actually the stars that are rotating). Nothing like human reality, the camera’s view of the night sky is equal parts beautiful and revealing. (Can you think of a faster, more effective way to demonstrate Earth’s rotation than a star trail image?)
Here are the factors that determine the amount of stellar motion:
- Exposure duration: The longer your shutter is open, the more motion your sensor captures.
- Focal length: Just as it is with terrestrial subjects, a longer focal length shrinks the range of view and magnifies the stars that remain.
- Direction of composition: Compositions aimed toward the North or South Poles will display less star motion than compositions aimed toward the celestial equator. That’s because, due to Earth’s rotation on its axis (the imaginary, infinite line skewering our North and South Poles around which our planet rotates), everything in the sky rotates 360 degrees in, around the poles, in 24 hours. But even though every star rotates the same number of degrees in any given period (seconds, minutes, hours, or whatever), the stars appear to travel different distances in that same period: The farther a star is from the axis of rotation (the North or South Pole), the more visual distance it covers to complete its 360 degree circuit (it appears to move faster). This is clear to see when you realize that the farther a star is from one of the poles, the longer its arc is in a star trail image.
Star Trails, Desert View, Grand Canyon National Park
As with water motion, you can choose between a long exposure that exaggerates stellar motion, or a shorter exposure that freezes the stars in place to display a more conventional night sky (albeit with more stars than our eyes can discern).
Read more in my Starlight photography Photo Tips article
Freezing motion
The other end of the motion continuum is stopping it in its tracks with an exposure of extremely short duration. Sometimes we simply want to avoid blurring something that should be stationary, like wind-blown flowers or leaves. But just as a long exposure can blur water to reveal patterns in its motion that aren’t visible to the unaided eye, using a short exposure to freeze a fast moving or ephemeral subject freezing can reveal detail that happens too fast for the unaided eye to register.
Stopping motion in an image often requires exposure compromises, such as a larger than ideal aperture or higher ISO, or removing a polarizer. In my landscape world, f-stop rules all, so I won’t compromise my f-stop unless depth is a non-factor—for example, when everything in the scene is at infinity at all f-stops. And I’m reluctant to remove a polarizer because its reflection-removing effect, even when minor, can’t be duplicated in Photoshop. Fortunately, compromising ISO is relatively painless given today’s digital cameras stellar high ISO capabilities.
Wind-blown leaves, breaking surf, and plummeting waterfalls are examples of detail that can be frozen in the act, but my favorite example of an instant frozen in time is a lightning strike. Lightning comes and goes so fast that the human experience of it is always just a memory—it’s gone before we register its existence. Read how to photograph lighting in my Lightning Photo Tips article.
So what’s the point?
In the static world of a photograph, it’s up to the photographer to create a sense of motion. Sometimes we achieve this with lines that lead the eyes through the scene, but even more powerful is an image that uses motion to tap its viewer’s imagination. Whether freezing an instant, or blending a series of instants in a single frame, the way you handle motion in your scene is a creative choice that’s enabled by your creative vision and technical skill.
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Wel said, Gary. I use longer exposure times on subjects other than water, such as crowds and traffic. I like how a quarter second, one second, etc. lengthens “the decisive moment” and allows me to perceive the world just a bit differently.
Thanks, Scott. Yes, long exposures are a great creative tool that give us control over the way our images convey motion (or hide it).
Great article. Can’t make up my mind. What is better your blog or your photography.
Thanks, John, I really appreciate that. Hope you and Kelly are doing well.
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Inspired by two GH workshops, I lead several beginner level classes for a local art school. I’m an avid GH blog reader, always on the lookout for ideas to stea- er, pass along. In my limited experience, motion blur is the best way to demonstrate the bridge between the technical and creative aspects of photography.; that is, how to use the camera as a tool.
I am always inspired by the clarity and precision of your explanations. They encourage me to strive me to be a better instructor and a better photographer.
I appreciate hearing that—and thank you for your positive words and support!
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