Clearing Storm in Twilight, Yosemite Valley
Canon EOS 5D Mark III
30 seconds
F/4.0
ISO 800
47 mm

I’d billed my just completed Yosemite spring workshop as a crescent moon workshop. The plan was (among other things) to photograph a crescent moon rising above Yosemite Valley in the pre-sunrise twilight on consecutive mornings. This spring waning crescent is one of my very favorite Yosemite phenomena, something I try not to miss each May (when it aligns best with Half Dome from the most accessible locations). But Mother Nature had other ideas. Instead of the reliably clear skies California typically enjoys in May, this year a stubborn low pressure system parked off the coast and pumped moisture into Northern California. But despite a pessimistic forecast that called for rain and lots of clouds, my hardy group rallied at 4:45 each morning to be in place in the unlikely event the moon showed.

For our first morning I’d plotted a location beside the Merced River to photograph a 12% crescent moon that would appear from behind Half Dome just before 5:15. But we pulled up to the spot to find that the clouds had swallowed Half Dome; we didn’t even get out of the cars. Instead we hightailed it to Tunnel View for the first of what would become many Yosemite Valley clearing storm experiences (that most Yosemite visitors can only dream about). By the time we arrived the sky had brightened significantly, the clouds above Half Dome had started to part, and wisps of mist swirled on the valley floor beneath Bridalveil Fall.

My plan for our second morning was to start at Tunnel View at around 5:00, exactly one hour before sunrise. I knew a 6% crescent moon would crest Sentinel Dome (between Half Dome and Cathedral Rocks) at 5:13 (+/- a minute or so), and wanted to give everyone enough time to set up in the dark. It was still quite dark when we arrived, with just enough light to know something special was happening in Yosemite Valley. I hustled everyone to the wall and assured them that their cameras would be able to accumulate enough light to reveal far more detail than our eyes could see.

To give you an idea of how dark it was when we started shooting, the image at the top of page is a 30 second exposure at f4 and ISO 800. If the sky had been clear when I clicked this frame, the moon would have been balanced atop Sentinel Dome, almost exactly as it was in May, 2008 (below). Contrast the above clearing storm exposure settings with the settings for my crescent moon image below: 5 seconds at f7 and ISO 200. Both were almost exactly 45 minutes before sunrise, but in the crescent moon image I intentionally underexposed the scene to hold the color in the sky (washed out to my eyes by the rising sun), hide foreground detail, and etch the distinctive outline of Half Dome and Sentinel Dome in silhouette. The clearing storm image, on the other hand, is actually slightly overexposed to reveal beauty hidden by the darkness in Yosemite Valley.

Lunar Kiss, Half Dome and Sentinel Dome, Yosemite

So if there’s a single takeaway from these two images, it’s that just as with our composition decisions, our exposure settings are creative choices allowing us to express the world in ways that are different, but no less true, than the human experience. Photography is most powerful when it can expand our perception of reality to reveal unseen or overlooked aspects of nature, whether it be the simple shapes of Yosemite Valley, or the hidden world before the sun.

A few words about night sky color

Before the inevitable “that color isn’t natural” comments, let me strike preemptively by addressing the common misconception that color is an inherent, exclusive quality of an object or scene. While color is indeed a defining characteristic, of equal importance is the light illuminating an object or scene. Just as the sky is blue at noon and orange at sunset, every scene in nature changes color throughout the day.

Color becomes a bit more problematic at night, when there isn’t light enough light for the cones in our eyes to register color. But that doesn’t mean the color isn’t there. Camera’s have many disadvantages compared to human vision, but one area where a camera excels is its ability to accumulate light. Using this capability, photographers can reveal a scene’s natural color by brightening the scene far beyond the human experience.

The night side of Earth is simply shadow, much like standing behind a tree (an extremely large tree). And as with the world behind a tree, all direct sunlight is blocked, leaving the shaded area illuminated solely by reflected light. Because sunlight’s shorter, violet and blue wavelengths are more easily reflected (sunlight’s longer wavelengths pass straight through to illuminate and warm Earth’s sunlit side exclusively), they’re the only wavelengths left to illuminate Earth’s night side. So, while the night sky looks black to our eyes, it is in fact quite blue. (And we have the images to prove it.)