Photograph: “Photo” comes from phos, the Greek word for light; “graph” is from graphos, the Greek word for write. And that’s pretty much what photographers do: Write with light.
Because we have no control over the sun, nature photographers spend a lot of time hoping for “good” light and cursing “bad” light—despite the fact that there is no universal definition of “good” and “bad” light. Before embracing someone else’s good/bad light labels, let me offer that I (and most other serious photographers) could probably show you an image that defies any good/bad light label you’ve heard. The best definition of good light is light that allows us to do what we want to do; bad light is light that prevents us from doing what we want to do.
Studio photographers’ complete control of the light that illuminates their subjects, a true art (that I’m in awe of), allows them to define and create their own “good” light. On the other hand, nature photographers, who rely on sunlight and weather’s fickle whims, don’t have that kind of control. We can plan and hope, but ultimately must accept what we get.
Fortunately, knowledge is power: The better we understand light—what it is, what it does, and why/how it does it—the better we can anticipate and be present for the light we seek, and adjust to whatever light we encounter.
Energy generated by the sun bathes Earth in continuous electromagnetic radiation, its wavelengths ranging from incomprehensibly short to incomprehensibly long (how’s that for specific?). Among the broad spectrum of electromagnetic solar wavelengths we receive are ultraviolet rays that burn our skin (10-400 nanometers), infrared waves that warm, among many other things, our atmosphere (700 nanometers to 1 millimeter), and the visible spectrum that allow us (and our cameras) to view the world—a very narrow range of wavelengths between ultraviolet and infrared with wavelengths that range between 400 and 700 nanometers.
When all visible wavelengths are present, we perceive the light as white (colorless). But when light interacts with an object, the object absorbs or scatters some of the light’s wavelengths. The amount of scattering and absorption is determined by the interfering object’s properties. For example, when light strikes a tree, characteristics of the tree determine which of its wavelengths are absorbed, while the wavelengths not absorbed are scattered. Our eyes capture these scattered wavelengths and send that information to our brains, which translates them into colors.
When light strikes an alpine lake, some is absorbed by the water, allowing us to see the water. Some light bounces back to the atmosphere to create a reflection. The light that isn’t absorbed or reflected by the water light passes through to the lakebed and we see whatever is on the lake’s bottom.
For evidence of light’s colors, look no farther than a rainbow. Because light slows when it passes through water, and shorter wavelengths slow more than longer wavelengths, water refracts (bends) light. White light (light with an evenly distributed array of the entire visible spectrum) entering a raindrop separates and spreads into a full range of visible wavelengths that we perceive a range of colors. When this separated light strikes the back of the raindrop, some of it reflects back to our eyes: A rainbow!
When sunlight reaches Earth, the relatively small nitrogen and oxygen molecules that are most prevalent in our atmosphere scatter its shorter wavelengths (violet and blue) first, turning the sky overhead (the most direct path to our eyes) blue. The longer wavelengths (orange and red) don’t scatter as easily continue traveling through more atmosphere—while our midday sky is blue, these long wavelengths are coloring the sunset sky of someone to the east.
In the mountains, sunlight has passed through even less atmosphere and the sky appears even more blue than it does at sea level. On the other hand, when relatively large pollution and dust molecules are present, all the wavelengths (colors) scatter, resulting in a murky, less colorful sky (picture what happens when your toddler mixes all the paints in her watercolor set).
Most photographers (myself included) generally avoid blank blue sky because clouds are interesting, while their absence is boring. Additionally, when the sun is overhead, bright highlights and deep shadows create contrast that cameras struggle to handle. That means even a sky completely obscured by a homogeneous gray stratus layer, while potentially as boring as blue sky, is generally preferred because it reduces contrast and softens the light (more below).
Remember the blue light that scattered to color our midday sky? The longer orange and red wavelengths that didn’t scatter overhead, continued on. As the Earth rotates, eventually our location reaches the point where the sun is low and the sunlight that reaches us has had to fight its way through so much atmosphere that it’s been stripped of all blueness, leaving only its longest wavelengths to paint our sunrise/sunset sky shades of orange and red.
When I evaluate a scene for vivid sunrise/sunset color potential, I look for an opening on the horizon for the sunlight to pass through, pristine air (such as the clean air immediately after a rain) that won’t muddy the color, and clouds overhead and opposite the sun, to catch the color.
Overcast and shade
Sunny days are generally no fun for nature photographers. In full sunlight, direct light mixed with dark shadows often forces nature photographers to choose between exposing for the highlights or the shadows (or to resort to multi-image blending). So when the sun is high, I generally hope for clouds or look for shade.
Flat gray sky or deep shade may appear dull and boring, but it’s usually the best light for midday photography. Clouds diffuse the omni-directional sunlight—instead of originating from a single point, overcast light spreads evenly across the landscape, filling shadows and painting the world in diffuse light. Similarly, whether caused by a single tree or a towering mountain, all shadow light is indirect. While the entire scene may be darker, the range of tones in shade are very easily handled by a camera.
When skies are overcast, I can photograph all day—rather than seeking grand landscapes, in soft overcast light I tend to look for more intimate scenes that minimize or completely exclude the sky. And when the midday sun shines bright, I look for subjects in full shade. Overcast and shade is also the best light for blurring water because it requires longer shutter speeds.
Another option for midday light is a high-key approach that uses the overexposed sky to help my subject stand out. Putting a backlit subject against the bright sky, I simply meter on my subject and blow out the sky to create a white background.
Whether I’m traveling to a photo shoot, or looking for something near home, my decisions are always based on getting myself to my locations when the conditions are best. For example, in Yosemite I generally prefer sunset because that’s when Yosemite Valley’s most photogenic features get late, warm light. Mt. Whitney, on the other side of the Sierra, gets its best light at sunrise, and I prefer photographing the lush redwood forests along the California coast in rain or fog. Though I plan obsessively to get myself in the right place, in the best light, sometimes Nature throws a curve, just to remind me (it seems) not to get so locked in on my subject and the general tendencies of its light that I fail to recognize the best light at that moment.
Click an image for a closer look, and a slide show.