question: Why is it easier to see through fog when you’re in a forest/surrounded by trees?
comment: It'd depend on how dense the fog is, and where/how bright any light sources are; but you're probably not actually seeing any better in a forest in comparison to a more level location like a field - you're just surrounded with more "landmarks" (like the trees) that help you perceive depth. That sense of depth helps you determine where you are, and develop a sense of scale that you won't have if there're less things to compare your location to.
passages: The international definition of fog is a visibility of less than ; mist is a visibility of between and and haze from to . Fog and mist are generally assumed to be composed principally of water droplets, haze and smoke can be of smaller particle size; this has implications for sensors such as Thermal Imagers (TI/FLIR) operating in the far-IR at wavelengths of about 10 μm which are better able to penetrate haze and some smokes because their particle size is smaller than the wavelength; the IR radiation is therefore not significantly deflected or absorbed by the particles. 
   Haze can be defined as an aerial form of the Tyndall effect therefore unlike other atmospheric effects such as cloud and fog, 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. Infrared (IR) imaging may also be used to penetrate haze over long distances, with a combination of IR-pass optical filters (such as the Wratten 89B) and IR-sensitive detector.
  
  Section::::See also.
  
  BULLET::::- Arctic haze
  
  BULLET::::- ASEAN Agreement on Transboundary Haze Pollution
  
  BULLET::::- Asian brown cloud
   What Tineo sees is a dense, obscuring fog in the center of his vision which, if the light is good, allows objects to appear as a blur, though with black turned white and white turned black, as in a photographic negative. If the light indoors or out is too bright, the fog turns into an intense and painful glare.
   The term "fog" is typically distinguished from the more generic term "cloud" in that fog is low-lying, and the moisture in the fog is often generated locally (such as from a nearby body of water, like a lake or the ocean, or from nearby moist ground or marshes).
  
  By definition, fog reduces visibility to less than , whereas mist causes lesser impairment of visibility.
  
  For aviation purposes in the UK, a visibility of less than but greater than is considered to be mist if the relative humidity is 95% or greater; below 95%, haze is reported.
  
  Section::::Formation.
   Visibility in a natural haze declines exponentially, not linearly, with distance, due to scattering. The colour of the light being scattered into the viewing path affects the colour of the haze; blue under blue skies, reddish near sunset, as with alpenglow. These more subtle details are represented in some graphics.
   Visibility perception depends on several physical and visual factors. A realistic definition should consider the fact that the human visual system (HVS) is highly sensitive to spatial frequencies, and then to use the Fourier transform and the contrast sensitivity
  
  function of the HVS to assess visibility.
  
  Section::::Fog, mist, haze, and freezing drizzle.
   Distance fog
  
  Distance fog is a technique used in 3D computer graphics to enhance the perception of distance by shading distant objects differently.
  
  Because many of the shapes in graphical environments are relatively simple, and complex shadows are difficult to render, many graphics engines employ a "fog" gradient so objects further from the camera are progressively more obscured by haze and by aerial perspective. This technique simulates the effect of light scattering, which causes more distant objects to appear lower in contrast, especially in outdoor environments.
   Rainfall tends to be highly seasonal, sparse, and far between, therefore fog interception is a significant water source during dry seasons. Throughout the year, wind speed, temperature, and humidity are fairly consistent, with humidity usually greater than 90%. At one study site in the Guajira Peninsula, dry season precipitation ranged from 1–4 days per month, while in the wet season, although increased, it was still a relatively low 4 to 12 days per month, supporting the idea that the majority of the water in this region is held in low cloud cover and fog interception. Sunshine duration is distributed bimodally and correlates with evaporation rates.
   Mist is commonly mistaken for fog. These two things are very different, however they do have some things in common. Fog and mist are both formed the same way. Fog is denser and generally lasts for longer but mist is thinner and you can see more clearly through it.
  
  Section::::Description.
   Shadows are cast through fog in three dimensions. The fog is dense enough to be illuminated by light that passes through gaps in a structure or tree, but thin enough to let a large quantity of that light pass through to illuminate points further on. As a result, object shadows appear as "beams" oriented in a direction parallel to the light source. These voluminous shadows are created the same way as crepuscular rays, which are the shadows of clouds. In fog, it is solid objects that cast shadows.
  
  Section::::Sound propagation and acoustic effects.
   Fog shadows may look odd to viewers who are not used to seeing shadows in three dimensions. A thin fog is just dense enough to be illuminated by the light that passes through the gaps in a structure or in a tree. As a result, the path of an object's shadow through the fog becomes visible as a darkened volume. In a sense, these shadow lanes are the inverse of crepuscular rays caused by beams of light, but caused by the shadows of solid objects.
   Fog also produces good tropospheric results, again due to inversion effects. Fog occurs during high-pressure weather, and if such conditions result in a large belt of fog with clear sky above, there will be heating of the upper fog level and thus an inversion. This situation often arises towards night fall, continues overnight and clears with the sunrise over a period of around 4 – 5 hours.
  
  Section::::Tropospheric ducting.
   Unlike local methods such as Phong shading, ambient occlusion is a global method, meaning that the illumination at each point is a function of other geometry in the scene. However, it is a very crude approximation to full global illumination. The appearance achieved by ambient occlusion alone is similar to the way an object might appear on an overcast day.
   Looming is most commonly seen in the polar regions. Looming was sometimes responsible for the errors made by polar explorers; for example, Charles Wilkes charted the coast of Antarctica, where later only water was found. 
  
  The larger the size of the sphere (the planet where an observer is located) the less curved the horizon is. William Jackson Humphreys' calculations showed that an observer could see all the way around a planet nearly six times larger in radius than the Earth, with the same atmosphere as the Earth, because of looming.
  
  Section::::Sinking.
   Cloud cover is often referred to as "mist" when encountered on mountains, whereas moisture suspended above a body of water or marsh area is usually called "fog". One difference between mist and fog is visibility. The phenomenon is called fog if the visibility is or less. In the U.K., the definition of fog is visibility less than (for driving purposes, UK Highway Code rule 226), while for pilots the distance is 1 km. Otherwise, it is known as mist.
  
  Mist makes a light beam visible from the side via refraction and scattering on the suspended water droplets.
   Around the outer periphery of this heavy fog is a thin rim of lighter fog through which, on a “good-eye day,” Tineo can occasionally make out images, contrasts and color. His brain receives this jumble of information and transforms it into visual hints coupled with memory that he has learned to assemble—like the pieces of a mosaic—into some semblance of vision.
   Nathaniel Dominy, an anthropology professor at Dartmouth College (Robert L. May's alma mater), published a scholarly paper on Rudolph's red nose in the open access online journal "Frontiers for Young Minds" in 2015. In the paper, Dominy noted that reindeer eyes can perceive shorter wavelengths of light than humans, allowing them to see ultraviolet light; ultraviolet light, however, is much more easily scattered in fog, which would blind reindeer. Thus, Rudolph's red nose, emitting longer-wavelength red light, would penetrate the fog more easily. A summary of Dominy's findings was released in an "Associated Press" article on December 22.
   Advection fog occurs when moist air passes over a cool surface by advection (wind) and is cooled. It is common as a warm front passes over an area with significant snow-pack. It is most common at sea when moist air encounters cooler waters, including areas of cold water upwelling, such as along the California coast ("see" San Francisco fog). A strong enough temperature difference over water or bare ground can also cause advection fog.
   Two large Blizzard franchises, "Warcraft" and "StarCraft", use a fog of war which only reveals terrain features and enemy units through a player's reconnaissance. Without a unit actively observing, previously revealed areas of the map are subject to a shroud through which only terrain is visible, but changes in enemy units or bases are not. This is also common in both turn-based and real-time strategy games, such as the "Total War" series, "Age of Empires" series, , "Advance Wars" series, "Fire Emblem" series and Sid Meier's "Civilization" series.
   Section::::Ultimate Causation Hypotheses.:Long-distance foliage hypothesis.
  
  This hypothesis suggests that trichromacy has evolved to adapt to distinguishing objects from the background foliage in long distance viewing. This hypothesis is based upon the fact that there is a larger variety of background S/(L+M) and luminance values under long-distance viewing.
  
  Section::::Ultimate Causation Hypotheses.:Short-distance foliage hypothesis.
   These factors are therefore important for defining the transmitting properties of a transparent material-
  
  Transmission – The amount of light that passes through the material without being scattered
  
  Haze – The amount of light that is subject to Wide Angle Scattering (At an angle greater than 2.5° from normal (ASTM D1003))
  
  Clarity – The amount of light that is subject to Narrow Area Scattering (At an angle less than 2.5° from normal)
  
  Section::::Measurement.
  
  Measurement of these factors is defined in two International test standards-
  
  ASTM D1003 – Comprising two test methods –
  
  Procedure A – using a Hazemeter
   Sinking is the opposite of looming. In sinking, stationary objects that are normally seen above the horizon appear to be lowered, or may even disappear below the horizon. In looming, the curvature of the rays is increasing, while sinking produces the opposite effect. In general, looming is more noticeable than sinking because objects that appear to grow stand out more than those that appear to shrink.
  
  Section::::Towering and stooping.
   In seasonally snow-covered zones, winter albedos of treeless areas are 10% to 50% higher than nearby forested areas because snow does not cover the trees as readily. Deciduous trees have an albedo value of about 0.15 to 0.18 whereas coniferous trees have a value of about 0.09 to 0.15. Variation in summer albedo across both forest types is correlated with maximum rates of photosynthesis because plants with high growth capacity display a greater fraction of their foliage for direct interception of incoming radiation in the upper canopy. The result is that wavelengths of light not used in photosynthesis are more likely to be reflected back to space rather than being absorbed by other surfaces lower in the canopy.
   Although strong winds often mix the air and can disperse, fragment, or prevent many kinds of fog, markedly warmer and humid air blowing over a snowpack can continue to generate advection fog at elevated velocities up to or more – this fog will be in a turbulent, rapidly moving, and comparatively shallow layer, observed as a few centimeters/inches in depth over flat farm fields, flat urban terrain and the like, and/or form more complex forms where the terrain is different such as rotating areas in the lee of hills or large buildings and so on. 
   Section::::Modern methods.:International use.
  
presuppositions: It's easier to see through fog when you're in the forest.  You can see through fog easier if you're surrounded by trees.
corrections: The difficulty to see depends on how dense the fog is rather than your surroundings.  You're probably not seeing any better through fog when surrounded by trees, you're just surrounded by more landmarks that help you preceive depth.
raw_presuppositions: It's easier to see through fog when you're in the forest.  You can see through fog easier if you're surrounded by trees.
raw_corrections: The difficulty to see depends on how dense the fog is rather than your surroundings.  You're probably not seeing any better through fog when surrounded by trees, you're just surrounded by more landmarks that help you preceive depth.