Assertion: camera's lense | /r/HasProperty | zoom lenses
Facets:
Source sentences:
text: Since it is harder to construct a lens that does not change focus with the same image quality as one that does, the latter applications often use lenses that require refocusing once the focal length has changed (and thus strictly speaking are varifocal lenses, not zoom lenses).
text: Some lenses, called zoom lenses, have a focal length that varies as internal elements are moved, typically by rotating the barrel or pressing a button which activates an electric motor.