Threshold contrast

{
  "id": "MLC-T-MET-009637",
  "term": "Threshold contrast",
  "field": "Meteorology and atmospheric science",
  "definition": "The minimum perceptible difference in luminance between an object and its background that allows an observer to detect the object 50 percent of the time. This value is a key factor in the theory of visual range and depends on the observer's visual acuity, background luminance, and the angular size of the object. Allard's law and Koschmieder's law use a standard threshold contrast value, typically 0.02, to calculate meteorological optical range from the atmospheric extinction coefficient.",
  "url": "https://mlchart.com/terminology/meteorology/threshold-contrast/"
}