Okay, so that’s pretty basic. How about this one?
Wikipedia: The change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated
Whoa, I hope that’s not on the test.
Who doesn’t love the soothing tranquility of a crisp reflection? And like a metaphor in writing, a reflection is an indirect representation that can be more powerful than its literal double thanks to its ability to engage the brain in different ways than we’re accustomed. Rather than processing the scene directly, we first must mentally reassemble the reflection’s reverse world, and in the process perhaps see the scene a little differently.
Reflections are a powerful photographic tool as well. Water’s universal familiarity makes it an ideal subject for photographers frustrated by their camera’s static representation of our dynamic world. Just as we freeze or blur a waterfall to express turbulent motion, we can include a reflection to convey serenity.
Water reflections come in many forms, from a mirror-sharp inverted mountain shimmering atop a still pool, to an abstract shuffle of color and texture on an undulating lake. Without getting too far into the physics of light, it’s important to understand that every object we see and photograph (that doesn’t generate its own light) comes to us courtesy of reflected light. For example, when sunlight strikes Half Dome in Yosemite, some of the sun’s photons bounce straight back into our eyes, and there it is.
But other photons head off in different directions—some are captured by other sets of eyes, while others land on the surface of the Merced River. Some of these photons penetrate the water to reveal the submerged riverbed, while others carom off at the same angle at which they struck the water, like a pool ball striking the cushion, or a hockey puck off the boards. The ricocheting photons that travel from Half Dome and bounce off the river, reach our eyes as a reflection. In other words, what we call a reflection is in fact re-reflected light (reflected first from El Capitan, then by the river).
The recipe for a mirror reflection
The ingredients for a crisp, mirror reflection is pretty simple: still water, a sunlit subject that’s much brighter than the water’s surface (the greater the contrast the better), and a view angle that matches the angle from the water’s surface to the reflection subject. (The best reflections are usually found on shaded water because there are fewer photons to compete with the photons bouncing from the reflected subject.)
In the image on the left, with El Capitan in direct sunlight but the slow moving Merced River still shaded, my biggest challenge was finding floating fall leaves to include with my reflection. Once I found this spot, my only option was to use my Sony 12-24 f/2.8 GM lens (on my Sony a7RIV body), which gave me a field of view just wide enough to fit El Capitan, Three Brothers, the reflection, and the floating leaves into my frame.
Playing the angles
Understanding that reflected photons leave the water’s surface at the same angle at which they arrive—imagine the way a tennis ball bounces (if it weren’t affected by spin, wind resistance, or gravity)—helps us get in position for the reflection we want.
A few years ago I found myself atop Sentinel Dome right after an intense rain shower had turned indentations in the granite into small, glistening pools. Rather than simply settle for the vivid sunset coloring the clouds above, I decided to include the sunset reflected in the pools as well. At eye-level the pools reflected blue sky, so I dropped my tripod as low as it would go, almost to granite level, positioning my lens at the same angle to the pools that the red light leaving the clouds struck the water.
When the water’s in motion
As spectacular as a crisp, mirror reflection in still water is, it’s easy to overlook the visual potential of a reflection that’s not crisp, or to forget your camera’s ability to render a soft or abstract reflection much better than your eyes view it. While a crisp reflection often dominates the primary subject in an image, a splash of reflected color or shape can provide a striking accent to a dominant primary subject. And a reflection that’s lost to the continuously varying angles of rippled or choppy water, magically appears when a long exposure smoothes the water’s surface.
In this image from Lake Wanaka on the South Island of New Zealand, all the ingredients were in place for a special sunset reflection until a light breeze disturbed the lake’s surface with gentle undulations. By attaching a Breakthrough 6-stop neutral density filter to my Sony 24-105 f/4 G lens (Sony a7RIII camera), I was able to achieve a 30-second exposure that complete smoothed the lake’s surface. While not a perfect mirror, the resulting reflection has a very pleasing soft, gauzy look. The long exposure smoothed the distant clouds as well.
Where to focus
An often misunderstood aspect of reflection photography is where to focus. Though it seems counterintuitive, the focus point of a reflection is the reflection subject, not the reflection surface. This isn’t such a big deal in a scene like the Half Dome reflection at the top of the post, where the focus point of everything of visual significance is infinity, but it’s a very big deal when you want both your reflection and rocks or leaves on the nearby water surface sharp.
The El Capitan reflection on the right is very different from the Half Dome reflection above, where the extreme depth of field ensured sharpness whether I’d focused on anything in the scene or on the reflection. But here the leaves that were my scene’s primary emphasis were just a couple of feet from my camera, while El Capitan was several thousand feet distant. Even though the leaves floated atop the El Capitan reflection, focusing on El Capitan would have softened the leaves. To increase my depth of field, I stopped down to f/18 and focused several feet into the foreground leaves, then magnified the image on my LCD to verify that all of the leaves were sharp. Though El Capitan is slightly soft, a soft reflection is far more forgivable than a soft foreground.
It seems that reflections often feel like a fortuitous gift that we just stumbled upon. But given that reflections are entirely beholden to the laws of physics, they’re far more predictable than many of the natural elements we photograph. Taking a little time to understand the nature of reflections, and how they’re revealed by a camera, enables photographers to anticipate their appearance.
Click an image for a closer look, and to view a slide show.