About: http://webisa.webdatacommons.org/61407724

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	They might focus to a concave surface at one focal length, fairly flat at a different focal length, and convex at yet another focal length.There is no such thing as a perfectly focusing lens.
http://www.w3.org/ns/prov#wasQuotedFrom	dpreview.com