Growing up on the east coast, I remember some of the dense fogs that used to happen in both autumn and winter. At the time, I didn't really appreciate the aesthetic quality of the fog, and how it could be used to create some fun images.
The challenge is that we are dealing with a natural condition that does not occur every day. What causes fog? Fog can be caused by one of two different conditions:
The temperature of the air and the dew point are the same. This is usually caused by the air cooling down to the dew point.
Open water evaporating on cold days. This actually has an effect on the dew point near the water causing it to raise.
There is one other factor that needs to be taken into account. That factor is wind. Wind will cause cool air and warm air to mix resulting in the fog "going away."
What all of this means is that we can actually predict when foggy conditions are going to occur. If we know of areas of open water in the winter time, then we have a relatively reliable source for fog. For example, the Mississippi River near Swan Park in Monticello MN is a great place to find morning fog.
The other thing we can do is watch the weather reports for when the air temperature and dew points will be close together. This will be a good indication of a potentially foggy day.
In order for fog to look it's best in a photo, we need to pay attention to the light. Ideally, we would want to find locations where the fog will be backlit.
This will cause the fog to stand out a bit more since the shadows will be darker and the fog will be brighter. It is important to pay attention to the histogram, since you will want to make sure that you can bring up some of the shadows a bit in post processing.
When the details are important, side light can also be used. Side light will cause the scene to be brighter, so it is important that there be some areas in the scene that are darker in order to allow the fog to stand out a bit. Notice in the next photo that the light is actually coming in at an angle slightly behind me.
When photographing foggy scenes, you need to work fast. Foggy conditions can change rapidly. I remember driving past a foggy late in the North Cascades in Washington several years ago. There was someone fishing out on the lake. I quickly pulled over, grabbed my gear and walked back down the lake to try and capture the scene. In the short amount of time that it took to get back to the lake the fog had completely disappeared.
In order to save time, there are a few camera settings that can be set ahead of time. First, shooting in foggy conditions means that you are shooting in very "cloudy" conditions. The reason for this is that fog is essentially a cloud that is on or near the ground. Begin by having your ISO set to 400. If the fog is really thick, or you are capturing images of wildlife, then begin around 1000. Next set your aperture to something in the range of f/8 - f/14. The reason for this is that the fog will make dust spots a little more noticeable. It is for this reason, that I tend to lean more towards f/8. The only thing that you need to worry about is shutter speed. Since foggy days tend to be calm days, having a slow shutter speed works as long as you are using a tripod.
Once you get a few shots that have a decent looking histogram, you can then work with your settings to get more creative. For example, the second photo in this post was taken with an ISO of 64, and an aperture of f/20. Why those settings? I thought it would be really nice to get the sunburst through the trees so I needed to have a small aperture. I also wanted to take advantage of the low ISO in order to be able to work with the shadows in post processing. The tradeoff was that I did need to remove several dust spots from the image which added to the amount of time editing.
The photo gallery below contains some of my favorite foggy images.
Interested in learning more?
Check out the workshops page to get more information about upcoming classes, workshops, and photo hikes.