Some people associate fog with inclement weather and avoid the outdoors. Not me. I grab my camera to create some extremely exciting images. Foggy conditions elicit moody and ethereal feelings. The light is diffused and even, but very flat. Knowing how to take advantage of this allows you to create great fog photos.
As compositional elements recede from the camera position, so does the intensity of their shape, color, and contrast. By placing a dominant subject in the foreground, it becomes the primary element. All other parts become secondary as they melt into the background in a wash of mist. When created properly, photographs made in the fog tend to be soothing.
Fog, especially when near larger bodies of water, harbors or coastal environments, can be so thick it’s referred to as "pea soup." I’ve experienced this along the Oregon coast, the fishing ports of New England and even in the low humidity of Colorado. In situations like this, I protect my equipment the same as if shooting in the rain due to the rapid buildup of water on my equipment. Carry a washcloth to periodically wipe down the front element, the camera body and viewfinder.
Fog can easily trick a camera’s meter. Straight metering of fog will create an underexposed image due to the high reflectivity of light. My standard compensation is +1 ƒ-stop. Depending upon its thickness, more may be necessary. Check the distribution of pixels on the histogram to make sure you don’t lose detail in the highlights or shadows. Bracketing in 1/2 stop increments is beneficial in that different exposures produce different effects. Become a weather watcher and the next time fog is predicted, immerse yourself in it with your camera.