Posted on December 14, 2016
One of Yosemite’s most underrated winter treats is the radiation fog that hugs the valley floor on cold, clear, still mornings. Unlike the advection fog that drapes the San Francisco Bay Area (among other places) when (relatively) warm, saturated air passes over the colder ocean and blows inland, radiation fog forms in place when plummeting overnight temperatures cause airborne water vapor to condense.
A sheltered valley with a cold river, soggy meadows, and a spongy forest floor, Yosemite Valley is ideal for the formation of radiation fog. Each winter, storms fill the Merced River and soak the meadows and forest. On nights when there’s no wind to mix the atmosphere, cold air sinks until it meets the water-laden air near the ground. Because cold air can’t hold as much water vapor as warmer air, and the air on the valley floor is completely saturated, the airborne water vapor condenses as soon as the air chills even slightly: Fog.
Often no more than a thin, gray veneer, in radiation fog that’s dense enough to obscure trees across a meadow, it’s sometimes possible to see stars or blue sky overhead. Viewed from a distance (for example, from Tunnel View), Yosemite’s radiation fog appears to be in constant motion, alternately engulfing and revealing treetops, sometimes rising hundreds of feet and completely disappearing in a matter of minutes. With no wind to move the fog, the reality is that what appears to be motion is primarily fog forming and dissipating in place. Yosemite’s radiation fog persists until the air heats enough to hold the available airborne moisture, or the wind picks up and mixes warmer air above with the colder, saturated air below.
About this image
Last Friday morning I went out to scout a new route to one of my favorite Yosemite spots, a bend in the Merced River upstream from Sentinel Bridge with view and reflection of Half Dome. My Yosemite Winter Moon workshop started that afternoon, but the original access here had been obliterated by major roadwork underway in Yosemite Valley, so I needed to make sure I could still get my group out here.
With very little time to spare, I originally left my camera bag in the car, but didn’t get too far before second thoughts sent me back for it. Good thing—after a few minutes of traipsing across crunchy snow, I made it out of the woods and to the river just in time to catch sunlight illuminating a diaphanous radiation fog. Shadows cast by sunlight passing through evergreen branches created a beam effect in the illuminated mist, while upstream a blanket of fog basked in golden sunlight.
The sun was about to disappear behind the granite ridge beneath Glacier Point and I new I only had a few more minutes of this spectacularly illuminated fog. At first I tried to position the sun behind the trees, but at this distance the treetops were so thin that very little blocking occurred and I ended up with a white blob of blown highlights. So I hustled over to the intersection of the ridge’s shadow with the sunlit ground and prepared for a sunstar. Every lens creates a different sunstar effect, some much better than others, and my Sony/Zeiss 16-35 f/4 is my favorite. Stopping down to f/16, I went to work. Moving with the sun so I was always straddling the shadow line, I was able to shoot for about five minutes before the entire beach was in shade and I was finished.
Posted on July 15, 2013
I have a story that doesn’t really have anything to do with photography, except maybe that the experience got me thinking about my relationship with trees, and the number of images I have where a tree or trees are the primary subject. That connection was made because my story, in which a tree stars prominently, happened on the morning that I photographed this oak tree (and the crescent moon and oak trees image in my previous post).
Here goes (not for the faint of heart)
I’ve been a daily runner for nearly 22 years. For many years it was 50 miles per week, no days off; in recent years I’ve toned it down to a more sane 3 to 5 miles per day, with an occasional day off. I run on city streets, sometimes in the dark, dodging vehicles often guided by chatting, texting, speeding, angry, and/or drowsy drivers. I’ve stampeded sheep in New Zealand, breathed textured air in India, and have been chased by dogs, soaked by rain, and pelted by hail. Once, a squirrel ran up my leg.
But, while there are clearly many dangers to worry about while running, trees are pretty far down the list. They’re large, stationary, with no reputation for aggressive behavior. Which might explain why, until last Wednesday, (like most runners) I’d never actually run into a tree. Not even close.
Wednesday morning was hot, much hotter than I prefer, but I’d gotten out early enough that the houses and trees on the east side of my route cast occasionally useful shade. While I normally run in the street (believe it or not, asphalt is quite a bit softer than cement), on this morning I spent lots of time on the sidewalk when it meant the difference between shade and sunlight. By about 2 1/2 miles into my planned 3-miles the shade was rapidly shrinking, forcing me to stray even farther onto the sidewalk for relief. And so it happened that I found myself just close enough to the yard side of the sidewalk that a deceptively aggressive palm tree was able take a swipe at me as I flashed by. (That’s my story and I’m sticking to it.)
In my defense, my arborous encounter was not a George of the Jungle face-plant; rather, the collision was more of a glancing blow, something a ninja might incur after deftly eluding an enemy’s death swipe. Nevertheless, it left my upper forearm with a gaping wound that pretty much stunned me with sudden pain and flowing blood.
While my first impulse to any injury has always been to pretend that nothing happened in the hope that nobody will notice whatever foolish thing I did to cause the injury, the blood dripping down my arm and trailing me on the sidewalk made that pretty much impossible. By the the time I reached the next intersection I was bleeding so much that I prayed there’d be no cars who might call 911 to report a crime (what would you do if you saw a bleeding man running down the street?). At home I had to warn my wife to prepare for something gruesome before I entered the room. Once we got it cleaned up, it was clear that what I had was not so much a cut as it was an excavation—somewhere on that palm tree is an almond-size chunk of my flesh.
Today, nearly a week later, this stupid thing is still bleeding (I probably should have gotten stitches), though it’s down to just a few drops on the dressing each time I change it. As with all my running injuries, I tend to ignore them and hope they’ll go away. (And I must confess to kind of relish the coolness factor associated with running down the street with a slight limp.) Unfortunately, in this case, despite the ugliness of the wound, nobody can see it when I’m running and there’s really nothing cool about my answer when I’m asked what happened. I suppose I could have claimed to gotten it in a knife fight with a competing photographer (say, contesting a small patch of prime Yosemite real estate); instead I opt for the high road and just fess up: I, uh, ran into a tree. In broad daylight. Sigh.
As I mentioned in my July 12 post, my plan for this night had been to photograph a pair of oak trees in the foothills beneath a crescent moon. But my buddy and I arrived early, so we drove a few miles down the road to another group of trees that I like to photograph. The throbbing in my arm, while chasing trees, that got me thinking that evening about the morning’s mishap in the context of my “regular” relationship with trees. I chuckled about how I can be hyper-aware of some trees, yet so oblivious to others. Maybe not life changing insight, but food for thought at least.
The sun just disappearing as we pulled up to this second group of trees. Hoping hoping to catch a sunburst, I jumped out of the car, set up my tripod, pulled out my graduated neutral density filter (two-stop hard), metered, focused, and clicked in maybe fifteen seconds. Fortunately I nailed the first click, because by the time I recomposed a horizontal frame, the sun was gone.