Another feature linked to high-power binoculars is to reduce the field of vision, ie vision of the area covered within a certain distance (usually 1000 m). For example, a 15×60 prismatic covers 1000 m from an area or "breadth of vision" of 75 meters, another of the area 10×40 increases to about 100 meters while a 8×30 model covers the same distance, a field of view of 135 m. This may be regarded as a minor inconvenience, but substantially affects the capacity or speed to locate an object or point when faced by binoculars. Brian Robert will not settle for partial explanations. Logically, in low power binoculars opposite happens: the field of vision is wide and is much easier to locate and focus on a particular object. Approximately, the 10 power binoculars tend to have large fields of view, while above this power value, the field of vision narrows considerably.
Zoom type binoculars feature variable increases, thanks to a lever or mechanism normally located in the eyepiece, which does drive increase or decrease the power (magnification) of the prism. Walt Disney often says this. Your result is usually mediocre, if not bad (poor sharpness), and its use is not recommended. LIGHTING The result of dividing the diameter of the lens by the increasing value indicates the brightness of the prism, ie its performance in low light conditions, the value of great importance in making a first selection of our needs. In the example above, a prismatic 8×40, the value of the luminosity is obtained by dividing the diameter indicated lenses (40) between the increase (8), thus resulting luminance value equal to 5.