Posted on May 30, 2012
Cascading Ferns, Russian Gulch Fall, MendocinoCanon EOS-5D Mark III81 mm.6 secondsF/11ISO 400
“Photography’s gift isn’t the ability to reproduce your reality, it’s the ability to expand it.”
(The fifth installment of my series on photographic reality.)
There’s probably no better example of the difference between a camera’s reality and yours than the way we handle motion. In my previous post I compared the camera’s ability to accumulate light to the serial, real-time processing of seamless instants we humans do. In a static world, given the right exposure a photographic image can be rendered fairly literally (missing dimension notwithstanding). But photograph a world in motion and wonderful things start to happen.
A slow shutter speed allows a sensor to record the position of everything it “sees” during the exposure, expanding one frame into a recreation of every instant of its capture. When the capture includes objects in motion, the result a scene very different from the human experience: Rushing water smoothes to white, wind-whipped flowers blur to color, and Earth’s rotation renders stars as parallel streaks of light.
Labeled as cliché and unnatural by people who don’t understand photography, blurred water gets a bum rap. The cliché part ignores the fact that most rapidly moving water photographed in the best light (shade or overcast) is virtually impossible to not to blur. The “unnatural” label just cracks me up—when asked, detractors reply that freezing the motion (the only other option) would be more natural, to which I reply (usually to myself only, tongue firmly clamped between teeth), how many times have you seen water drops frozen in midair? The truth is, the camera and human eye handle motion differently, and photographers need to accept and appreciate it. Once you can accept that blurring water is often the best way to imply motion in a static medium, the fun begins.
First you need to understand that you can’t just blur every moving river, stream, or wave. Motion blur requires a slow shutter speed, impossible with water in full sunlight without a neutral density filter to cut the light. So you need to start by finding moving water darkened by overcast or shade (any sunlight in the frame at all will overexpose and likely ruin the image). Whitewater is best; if you find yourself photographing whitewater in shade or overcast, the question isn’t how to blur, it’s how much?
Unfortunately there’s no magic shutter speed for motion blur. The amount of blur you get depends on the speed of the water, how close you are to the water, how much you’re zoomed, and the angle of your capture relative to the direction of motion (and maybe some other things I’ve overlooked). And while there isn’t a ideal amount of blur, I find that there’s sweet spot (that changes with all the variables above) between very slight blur that’s not quite enough and just appears scratchy, and extreme blur that’s pure white. In some tight compositions of extremely fast water you get beautiful slight blur at 1/1o second; with wider compositions and/or slower water, the same amount of blur requires 3/4 second or longer. And achieving noticeable blur in a wide capture of a distant waterfall may require several seconds of exposure. My advice is to bracket your shutter speeds, varying your ISO and/or f-stop (take care that you don’t choose an f-stop that compromises your depth of field)—you’ll find the more you do it, the more you’ll get a sense for what works.
In the image of Russian Gulch Fall near Mendocino (at the top of the post), I arrived early enough to allow a full two hours to work the scene before sunlight blighted the forest floor. And work it I did, starting wide and trending tighter as I became more familiar with the scene. The dense forest dark didn’t allow a fast enough shutter speed for effective slight blur without severely compromising ISO and aperture (depth of field), so I just went with the extreme blur. Even though the air seemed perfectly still, I was a little concerned about slight wind motion in the ferns, so I bumped to ISO 400 and f11 (at 80 mm, f11 gave me about a 15 foot range of front-to-back sharpness–just enough). This resulted in a one second exposure that caused extreme blur (I call it extreme because I didn’t notice much difference between one second and five seconds) that, as it turned out, made the delicate strands of water quite lovely.
One other often overlook component of a forest water scene is a polarizer: I wouldn’t even attempt a scene like this without the glare reducing benefit of a polarizer. (And a polarizer has the added bonus of reducing the light by a couple of stops.)
Bristlecone Star Trails, White Mountains, California
Star trails—parallel streaks of light caused by Earth’s rotation during a long exposure–are an extreme example of the same motion effect that blurs water. I find that moonless nights work best for star trails—a moonlit sky is usually too washed out for effective star trail photography, while the limited light of a moonless night maximizes the motion by allowing even the dimmest stars to shine through.
On a moonless night, a large aperture and high ISO can record enough light to allow a relatively fast 30-second shutter speed that records stars as near pinpoints of light, but doesn’t allow enough light to fully eliminate the foreground. On the other hand, a slower shutter speed that accumulates enough light to reveal the foreground also results in streaking stars—star trails. An added advantage of star trail photography is that the exposures are long enough to enable a smaller aperture (more DOF and better image quality) and lower ISO (less noise).
Some people have great success combining a series short-exposure frames to create a single star trail image, but all of my images are single-click capture (that’s just me, I have no problem with those who choose to blend multiple captures) using a trial and error approach I’ve worked out over the years. I start by taking a test (throw-away) exposure at my camera’s highest ISO and lens’s widest aperture, then tweaking the exposure and repeating until I get it right. I’ve also found that in the near total darkness of a moonless night, these test exposures are the best way to ensure my composition and focus are okay. Once I have my exposure, composition, and focus right (it usually takes two or three images), I figure out how many stops of light my desired shutter speed (usually around thirty minutes) adds to my successful test exposure, then subtract an equal amount of light through a combination of aperture and ISO reductions. (I’ll try to post a more thorough tutorial on my approach to star trails soon.)
I photographed the above bristlecone pine against backdrop of streaking stars with three friends who were light painting the tree—sweeping the beam of a bright flashlight across the trunk and branches for the first few seconds of exposure to illuminate the tree’s weathered wood enough for their cameras to capture the exquisite detail. But all my images use only natural light, so I opted for a silhouette, positioning myself as low as I could get to juxtapose as much of the tree against the sky as possible. I started my exposure as soon as the others’ light painting ended (no more than ten seconds), and for the next twenty-two minutes the four of us reclined there at nearly 11,000 feet, watching the sky and waiting for the exposure to complete. We talked and laughed some, but mostly we just appreciated a sky dense with stars and silence so complete (and foreign) that it almost hurt my ears. We were well down the road toward our hotel in Bishop before my camera finished its processing, and it wasn’t until I was able to view the image on my laptop that I knew I’d had a success.
Category: How-to, stars Tagged: blurred water, bristlecone pine, night, Photography, star trails, waterfall
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