page_title: Least distance of distinct vision
hierarchical_section_title: Least distance of distinct vision
caption_attribution_description: Focal length Español: El foco F y la distancia focal f de una lente positiva, una lente negativa, un espejo c&#243;ncavo, y un espejo convexo. English: The focus F and the focal length f of a positive lens, a negative lens, a mirror concave and convex mirror.
context_page_description: In optometry, the least distance of distinct vision or the reference seeing distance is the closest someone with "normal" vision can comfortably look at something. In other words, LDDV is the minimum comfortable distance between the naked human eye and a visible object.
  magnifying power of a lens with focal length when viewed by the naked human eye:
context_section_description: In optometry, the least distance of distinct vision (LDDV) or the reference seeing distance (RSD) is the closest someone with "normal" vision (20/20 vision) can comfortably look at something.  In other words, LDDV is the minimum comfortable distance between the naked human eye and a visible object.
  magnifying power (M) of a lens with focal length (f in millimeters) when viewed by the naked human eye:
caption: The focal point F and focal length f of a positive (convex) lens, a negative (concave) lens, a concave mirror, and a convex mirror.
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