Lub varifocal CCTV lens yog ib hom koob yees duab lens uas tso cai rau kev hloov pauv focal ntev. Qhov no txhais tau hais tias lub lens tuaj yeem hloov kho kom muab lub kaum sab xis sib txawv, tso cai rau koj kom zoom hauv lossis tawm ntawm ib qho kev kawm.
Varifocal lo ntsiab muag feem ntau siv rau hauv lub koob yees duab kev ruaj ntseg vim tias lawv muab kev yooj yim ntawm kev saib. Piv txwv li, yog tias koj xav tau saib xyuas thaj chaw loj, koj tuaj yeem teeb lub lens rau lub kaum sab xis kom ntes ntau qhov chaw. Xwb, yog tias koj xav tau tsom mus rau thaj chaw tshwj xeeb lossis cov khoom, koj tuaj yeem ua kom zoom kom pom ze dua.
Piv nrog rau cov lo ntsiab muag ruaj khov, uas muaj ib qho, zoo li qub focal ntev, varifocal lo ntsiab muag muaj ntau yam ntxiv nyob rau hauv cov nqe lus ntawm kev tso lub koob yees duab thiab qhov chaw npog. Txawm li cas los xij, lawv feem ntau kim dua li cov lo ntsiab muag ruaj khov, thiab xav tau kev hloov kho ntau dua thiab ntsuas kom ntseeg tau tias kev ua haujlwm zoo.
Raws li piv rau aparfocal("tseeb") zoom lens, uas tseem nyob rau hauv kev tsom xam raws li lub lens zooms (focal ntev thiab magnification hloov), lub varifocal lens yog lub koob yees duab lens nrog qhov sib txawv focal ntev nyob rau hauv uas tsom hloov pauv raws li focal ntev (thiab magnification) hloov. Muaj ntau lub npe hu ua "zoom" lo ntsiab muag, tshwj xeeb tshaj yog nyob rau hauv cov koob yees duab ruaj khov, yog qhov tseeb varifocal lo ntsiab muag, uas muab cov qauv tsim lub lens ntau qhov yooj yim hauv kev tsim kho qhov muag (focal length range, siab tshaj plaws aperture, loj, hnyav, nqi) tshaj parfocal zoom.