Focus

fō′kus, n. ( opt. ) a point in which several rays meet and are collected after being reflected or refracted, while a virtual focus is a point from which rays tend after reflection or refraction—the principal focus is the focus of parallel rays after reflection or refraction: any central point:— pl. Fō′cuses , Foci (fō′sī). — v.t. to bring to a focus: to concentrate:— pa.p. fō′cu ed. — adj. Fō′cal , of or belonging to a focus.— v.t. Fō′calise , to bring to a focus: to concentrate.— n. Focimeter (fō-sim′e-tėr), an instrument for a isting in focu ing an object in or before a photographic camera—usually a lens of small magnifying power.— Focu ing cloth , a cloth thrown over a photographic camera and the operator's head and shoulders to exclude all light save that coming through the lens.— Conjugate foci , two points so situated that if a light be placed at one, its rays will be reflected to the other; In focus , placed or adjusted so as to secure distinct vision, or a sharp, definite image. [L. focus , a hearth.]