We’ve all heard it: “That’s so fake,” or “You Photoshopped that,” or some other derisive barb implying that an image is trying to be something it isn’t. But before you say that about this image, let me say that I processed it five times, each time dialing down the saturation, attempting to create something that would appear credible to the dubious masses. And with each pass, the color looked a little less like what we saw this unforgettable New Zealand morning. So finally I just said, enough is enough—you’ll just have trust me when I tell you that for the sake of credibility, you’re already being cheated of that morning’s full spectacle.
Don Smith and I got our New Zealand winter workshop group up early to photograph sunrise at the famous Wanaka willow tree. The tree was just a short walk from our hotel, and even though we still had 45 minutes until sunrise, it was apparent the second we stepped outside that something special was in store. Though it was still dark enough to require flashlights, already the entire sky radiated a rich ruby red. Since we’d shown the group the tree the prior afternoon, a few rushed ahead, but Don and I held back with the stragglers. Nevertheless, even the stragglers pace quickened as the red deepened, and by the time we reached the tree we were pretty much jogging.
Turns out we needn’t have rushed. For the next 30 minutes the red intensified until everything in sight seemed to buzz with color. I’ve experienced color like this a few times in my life, and the best way to describe is that it feels like the light possesses a physical component that penetrates my skin and everything else it touches. And with the sky throbbing in all directions, I felt like I might get dizzy whirling about to avoid missing something. Soon we all just started laughing at how unbelievable the show was, knowing that every picture we shared would be met with the obligatory “That’s so fake” skepticism.
All this got me thinking again about what causes color in the sky, so I dusted off a post I wrote a few years ago, tweaked a few things, and…
A sunset myth
If your goal is a colorful sunset/sunrise and you have to choose between pristine or polluted air, which would you choose? If you said clean air, you’re in the minority. You’re also right. But despite some pretty obvious evidence to the contrary, it seems that the myth that a colorful sunset requires lots of particles in the air persists. If particles in the air were necessary for sunset color, Los Angeles would be known for its incredible sunsets and Hawaii would only be known for its beaches.
But what is the secret to a great sunrise or sunset? Granted, a cool breeze, warm surf, and a Mai Tai are a great start, but I’m thinking more photographically than recreationally (sorry). I look for a mix of sky (to pass the sunlight) and clouds (to catch the color), with a particular emphasis on a clear horizon in the direction of the sun. But even with a nice mix of clouds and sky, sometimes the color fizzles. Often the missing ingredient, contrary to common belief, is clean air, the cleaner the better. And like most things, it all makes sense when you understand what’s going on.
Light and color
Understanding sunset color starts with understanding how sunlight and the atmosphere interact to make the sky blue. As you probably know, visible light reaches our eyes in waves of varying length, with each wavelength perceived as a different color. Starting with the shortest wavelengths and moving toward the longest, visible light goes from violet, indigo, blue, green, yellow, orange, and red. (These color names are arbitrary labels we’ve assigned to the colors we perceive at various points along the visible portion of the electromagnetic spectrum—there are an infinite number of colors in between each of these colors.) When a beam of light passes through a vacuum (such as space), it moves in a straight line, without interference, so all its wavelengths reach our eyes simultaneously and we perceive the light as white.
Why is the sky blue?
When light interacts with a foreign object—for example, when a beam of sunlight enters our atmosphere—different wavelengths respond differently depending on the size of the molecules they encounter. If sunlight encounters molecules that are larger than its wavelengths, such as atmospheric impurities like dust or smoke, all of the wavelengths bounce off (reflect). Because these large molecules are of varying sizes, a variety of wavelengths (colors) get blended into a murky sky with a gray or brown cast. If all the wavelengths get bounced equally, the sky will appear white(ish).
When a beam of sunlight hits the much smaller molecules of the gases that comprise our atmosphere (such as nitrogen and oxygen), some of its wavelengths are absorbed while others are reflected and scattered in all directions. Because the shorter wavelengths (violet and blue) scatter most easily; the longer wavelengths (orange and red) continue on to color the sky of someone farther away. The more direct the sunlight’s path to our eyes, the less atmosphere it passes through and the more we see the first (blue) wavelengths to scatter. When the sun is high in our sky, its light takes the most direct path through the atmosphere and our sky is most blue (assuming no pollutants have altered the scattering). In the mountains, sunlight has passed through even less atmosphere and the sky appears even more blue than it does at sea level.
When the sun is on the horizon, the light that reaches us has traveled through so much atmosphere that at the very least it has been stripped of its blueness because the blue wavelengths are the first to scatter (those wavelengths are coloring the sky of someone whose sun is high overhead). And if that sunrise/sunset light hasn’t encountered larger dust and smoke molecules on its journey, only the red wavelengths will have survived unscathed, and everyone enjoys the show.
The cleaner the air, the more vivid the sunrise/sunset color. To understand the mixing effect that happens when a variety of wavelengths are bounced around by large airborne particles, think about blending a smoothie consisting of a variety of brightly colored ingredients (such as strawberries, blueberries, and spinach—yum). Your smoothie’s color won’t be nearly as vivid as any of its ingredients, not even close. Instead you’ll end up with a brownish or grayish muck that might at best be slightly tinted with the color of the predominant ingredient. That’s what happens to the color when the light has to interact with large airborne particles like dust, smoke, and smog. Because these particles aren’t of uniform size, they each reflect a slightly different color rather than allowing one vivid color to dominate. In the middle of the day pollution means less blue; at sunrise/sunset, it’s less pink, red, and orange.
Clouds can enhance sunrise/sunset color by catching the red wavelengths and reflecting them back to our eyes, but only if there’s an opening on the horizon for the light pass through. Without clouds, the red wavelengths continue on to color the horizon opposite the sun—a “twilight wedge” when the color is in the sky, and “alpenglow” when mountains jut into the colored region of the sky and take on the color themselves.
So. To the skeptics who reflexively dismiss pictures like this, you might want to suggest that they spend more time out in nature. Whether it’s a tropical bird, a fluttering butterfly, a field of wildflowers, or a New Zealand sunrise, there really is nothing subtle about color in nature.