Haze and Fog

Some thoughts on haze and fog in photos

We have all admired and enjoyed superb Western landscape photographs with every detail tack sharp and crystal clear. Here in the Southeast only photos of nearby vista can come close to such quality.

When the next ridge is included invariably there will be hazy. Haze and frequent fog is what gave the Smoky Mountains their name.

Haze and fog can break a photo, but they can also make a photo.

So what is fog, what is haze? There are plenty of sources that explain the fine details of those phenomena. Fog consists of tiny water droplets – same stuff that makes clouds. Haze hereabouts is even smaller particles, mostly “volatile organic compounds” from the abundant vegetation, dust, and smoke. All these particles floating in the air scatter light in all directions. The smaller the particles the less they scatter light on the red end of the spectrum and thus look bluish. The more air volume, or distance, between the camera and the landscape, the more there will be of these particulates and the more light will we scattered into the picture. For haze it becomes noticeable over distances of miles, while the larger water droplets of fog act in just yards or feet. The image will look as if some added white or bluish light is added to the view.

Fog in particular does even more than that. The scattered light illuminates the scenery from all directions. There are no shadows. Textures are washed out. Dark objects are overlaid with the added white light, the blacks are thus eliminated. Fog can become dominant an confuse the light meter into setting the exposure so the fog becomes “average gray”, and all the darker details are underexposed.

Here is an example as viewed in a photo editor – ON1 Photo RAW in this case.

Let’s take a closer look at the histogram.

Notice that there is no data for a significant part at the black, left end, and none at the white, right end. There are no blacks or deep shadow area. Similarly, there are no bright areas. This makes the photo dreary and washed out looking. It is dark as well. Just not what the actual scene was like.

So for the first step to improve the photo is to “stretch the histogram”. In this editor this can be done with the Exposure slider, moving it to the right until the data in the histogram reaches the right end. Of course, the attentive photographer would take care of that when taking the photo by adjusting the exposure, either manually or with the compensation control. But, hey, who remembers those little details?

The other end is not so easily taken care of in the camera. In the editor the Black slider is moved to the left to stretch the data all the way to the left end.

Maybe a few more tweaks and we have a nice photo.

Note how the lower left corner, almost totally black anchors the visual range of the tones. The white clouds at the top complete the range so we can see the foggy scene realistically. Oh, sure, we can even “adjust” the amount of the fog to suit how the image should be presented.

Now let’s take a look at those hazy distant hills.

If fog and haze is just added white, or bluish, light, can’t we subtract an equal amount of blue, green, and red from each pixel and get rid of the haze? Well, that can be done, sort of. Many editors in fact have a haze slider. Let’s see what it does.

Here again the ON1 Photo RAW editor is used to show the effects of the Haze slider.

Moved to the left, the Haze slider reduces the amount of haze. If you allow it to work on the whole image it will affect other areas, not necessarily in a beneficial way. Look what it does to the clouds. Note the slider position marked with the yellow pointer (lower right).

The first illustration shows the Haze slider in the default, neutral (0) position. Haze is removed when the slider is moved left. the top right image shows it is moved halfway to the left (-50), bottom left all the way left (-100). The last image shows the Haze slider all the way to the right (+100) – adding more haze.

Careful use of this control can make a photo more like what the photographer saw and wants to share. I prefer to keep the haze pretty much the way the camera saw it.

If you have any thought, please share them in the comments.