The biggest problem with photographing landscapes in the fog is actually predicting when there will be fog. And while timing, location, and a little luck are important, an understanding of the types and causes of fog may help lift the veil and put you, and your camera, in the right place at the right time.
But before we get into the details, why would you want to shoot in the fog anyway? For me, fog provides a softness or ethereal feeling that adds interest to the landscape. It's the unknown, the mystery. Fog can also obscure unwanted backgrounds and help to isolate a subject. But it really is that otherworldly feeling that gets me excited.
So then what is fog? It might help to think of it as clouds at ground level. Made up of condensed water droplets which are the result of air being cooled to the point where it can no longer hold all the water vapor it contains.
There are four types of fog.
Radiation fog is formed on clear nights with relatively little or no wind present and usually forms in low-lying areas like mountain valleys. Radiation fog usually burns off as the sun and temperature rises.
Advection fog is when a layer of warm, moist air moves over a cool surface and is most common in coastal areas where sea breezes blow the air over cooler landmasses.
Upslope fog happens when moist stable air is forced up sloping land like a mountain range. Unlike radiation fog, upslope and advection fog may not burn off with the morning sun and may persist for days.
And finally, steam fog forms when cold, dry air moves over warm water and as it rises, resembles smoke. It is most common over bodies of water during the coldest times of the year.
Understanding the types of fog and when they might occur may help you to predict when and where it will happen. Or like me, you might just get lucky.
And unlike John Carpenter's movie "The Fog", you probably won't encounter any vengeful ghosts of shipwrecked mariners, but the fact that you don't know for sure is what will add interest to your photographs. And if it adds interest for you, then it will certainly add interest to viewers of your photography.