The international definition of fog is a visibility of less than 1 kilometer (3,300 ft); mist is a visibility of between 1 kilometer (0.62 mi) and 2 kilometers (1.2 mi) and haze from 2 kilometers (1.2 mi) to 5 kilometers (3.1 mi).
Fog and mist are generally assumed to be composed principally of water droplets, haze and smoke can be of smaller particle size.
The visibility problem
A known problem inherent in surveillance and other observation systems is the need to overcome visibility reducing conditions such as: humidity, haze, fog, mist, smoke, dust, snow or rain that might be present in the space between the surveillance system and the target being observed. The particles or droplets reduces visibility in two ways; the first is the actual obscuring of what is behind the particle, and the other is the effect called “light scattering” caused by light reflection in the particles.
Both these effects increase with distance, especially when zooming in on a distant object. Even on what appears to be a fine and clear day, there will most certainly be enough haze or fog in the air to reduce contrast significantly.
Haze differs slightly from clouds and fog as it can be defined as an aerial form of the Tyndall effect. Haze is spectrally selective: shorter (blue) wavelengths are scattered more, and longer (red/infrared) wavelengths are scattered less. For this reason many super-telephoto lenses often incorporate yellow filters or coatings to enhance image contrast.
Also, if using telephoto lenses there is an extra optical problem. Those lenses have a narrow field of view, allowing bright light outside your image area to affect your image with flare, which reduces contrast.
All these effects are drastically reduced with LYYN products.
Some clips recorded live with a LYYN unit: