Medicine:Least distance of distinct vision
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The focal point F and focal length f of a positive (convex) lens, a negative (concave) lens, a concave mirror, and a convex mirror.
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.[1] In other words, LDDV is the minimum comfortable distance between the naked human eye and a visible object.
The magnifying power (M) of a lens with focal length (f in millimeters) when viewed by the naked human eye can be calculated as:
- [math]\displaystyle{ {M} = \frac{250}{f}. }[/math]
See also
References
- ↑ Katz, Milton (August 1996). "Convergence Demands by Spectacle Magnifiers" (in en-US). Optometry and Vision Science 73 (8): 540–545. doi:10.1097/00006324-199608000-00004. ISSN 1538-9235. PMID 8869985. https://journals.lww.com/optvissci/Abstract/1996/08000/Convergence_Demands_by_Spectacle_Magnifiers.4.aspx.
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