What a Telephoto Lens Can Do With a Sea of Fog

A telephoto lens pointed at a sea of fog turns one broad, washed-out view into dozens of small pictures: a single ridge, a clump of treetops, a slow waterfall of mist spilling over a hill. Fog shifts by the minute and the best light on it can vanish in seconds, so the decisions you make before anything happens determine whether you come home with frames or just a nice morning.

Working the morning and evening fog around the Bay Area, Michael Shainblum spends nearly all his time on a 100-400mm zoom, using the long end to isolate bits of tree line poking out of the marine layer. His shutter speed rule is simple: he sets it to about double the focal length, so at 400mm he's near 1/800 s. That keeps the texture of the fog crisp and leaves him free to shoot handheld when the tripod slows him down. Aperture gets less thought. At f/8 with everything sitting at infinity, he points out, the shot looks the same no matter which f-stop you pick, and he only stops down further once foreground trees enter the frame and the scene spans more depth.

The first dramatic light of the morning lasted a few seconds, and Shainblum got exactly one frame out of it. He liked the tree on the left edge and the diagonal the fog drew across the scene, yet the middle felt thin without more treetops breaking the surface. So he turned to a different composition with less glow and better layering, then brought some nearby bushes into the frame at a wide aperture so they blurred into a soft green border. A little later, a swoop of fog dipped down on his right, and he took that one in a much darker, moodier direction.

San Francisco's summer fog is advection fog. It forms when moist Pacific air passes over the cold California Current, cools to its dew point, and gets drawn inland as the Central Valley heats up, which is why it tends to peak from June through August. It usually sits beneath a temperature inversion, a layer of warm air that caps the cool, damp air below and gives the fog its flat, defined top. That cap explains why walking uphill can pull you out of a gray blanket and into clear light within minutes. The same setup produces autumn valley fog, morning mist over lakes, and cloud seas in the mountains, so the approach travels well beyond the Bay. Cloud-base forecasts in apps such as Windy, along with GOES satellite loops, can help you guess whether a given overlook will be buried or sitting above the layer before you set an alarm. A long lens rewards that planning, since you can shoot distant ridges from wherever the fog line happens to settle.

For sunset, Shainblum set up facing a fog wave rolling in off the ocean, with a tree line low in the distance. He kept a circular polarizer on the lens, and at roughly 90° from the sun, a twist adds contrast to the sky behind the fog and to the detail within it. His plan was to shoot clean, short exposures first, then switch to a 10-stop ND filter and smooth the texture out completely to see how the mood changes. He also spent part of the evening watching one patch of trees for a bird, and only one ever flew through, which he caught. As the sun dropped low, he shot his first bracketed exposure of the trip, keeping the trees as silhouettes while holding detail in the bright sky and the shadows around the fog.

The next sunrise brought fog moving the opposite way, pouring over the hills from the east instead of drifting in from the west. Out past it, ridges like Wolfback Ridge, San Bruno Mountain, and the Marin Headlands rose like islands, with Sutro Tower standing above the layer. He ran a time-lapse on the same zoom at a 1-second interval, since the fog was moving quickly, planning on anywhere from 400 to 800 frames. While that ran, he kept scanning one section where a strip of land sat above a larger one, with fog spilling between them and bits of tree line appearing and disappearing in the twirls.

Shainblum's long-exposure versions of the fog are in the video above.