Assertion: camera lens's length | /r/Synonym | effective focal length
Facets:
value: often
type: TEMPORAL
value: to distinguish it
type: PURPOSE
value: for a thick lens
type: PURPOSE
Source sentences:
text: For a thick lens (one which has a non-negligible thickness), or an imaging system consisting of several lenses or mirrors (e.g. a photographic lens or a telescope), the focal length is often called the effective focal length (EFL), to distinguish it from other commonly used parameters: