Ib lub lens varifocal yog lub lens nrog lub ntsej muag kho qhov ntev. Cov cuab yeej ntawm hom no yog siv hauv cov koob yees duab (lawv tau nruab tshwj xeeb nrog cov lo ntsiab muag ntawm hom no) thiab cov koob yees duab yees duab (lawv tuaj yeem ua nrog qhov ntev focal ntev lossis nrog qhov sib txawv). Lub varifocal lens muaj ib qho kev kho qhov muag ib leeg, cov khoom ntawm cov khoom uas tau hloov pauv mus rau ib leeg, ua rau muaj kev hloov pauv (kho) ntawm lub focal ntev thiab, raws li, cov duab teev nyob rau hauv qhov ntau ntawm focal lengths. Txawm li cas los xij, lub sharpness ntawm lub aiming ntawm cov khoom thiab tus txheeb ze aperture tsis hloov.
Manually adjustable varifocal lens tso cai rau koj hloov lub focal ntev ob zaug, uas ua rau nws muaj peev xwm kho lub koob yees duab lub kaum sab xis ntawm saib rau cov duab zoo. Cov khoom siv nrog cov chaw taws teeb tswj tuaj yeem hloov qhov focal ntev ntawm 6 txog 50 zaug. Cov lo ntsiab muag zoo li no yog siv rau kev soj ntsuam video.
Cia saib dab tsi yog qhov zoo thiab qhov tsis zoo ntawm cov cuab yeej xws li lub lens varifocal.
Qhov zoo ntawm cov cuab yeej suav nrog qhov tseeb tias nws tso cai rau koj los kho lub kaum sab xis saib ncaj qha ntawm qhov chaw, thaum txhim kho lub koob yees duab yees duab. Thiab, ntawm chav kawm, tom qab kev txhim kho lub koob yees duab, nws muaj peev xwm kho qhov focal ntev. Qhov no yog qhov zoo ntawm cov khoom siv no kawg. Tam sim no cia peb mus rau qhov tsis zoo.
Lub koob yees duab nrog lub lens varifocal yuav tsum tau hloov kho, uas tsis yog ib txwm yooj yim, vim koj yuav tsum nqa cov cuab yeej ntxiv nrog koj tas li (kuaj saib, roj teeb, thiab lwm yam). Kev teeb tsa lub lens yog qhov nyuaj heev, nws yog ib qho tsim nyog los txiav txim siab qhov zoo ntawm qhov sib piv ntawm focal ntev thiab sharpness, thiab ib tug txheej txheem yog ua nrog tshwj xeeb lim (kub heev) uas darken daim duab. Yog li thawj qhov downside yog qhov teeb meem nyuaj.
Ib lub lens varifocal muaj qis dua (aperture) dua li lub lens ruaj. Qhov no tshwj xeeb tshaj yog pom ntawm cov khoom siv nrog ntau yam (5-50), cov duab zoo thaum tsaus ntuj yuav qias neeg. Tsawg aperture yog qhov teeb meem thib ob.
Qhov thib peb qhov tsis zoo ntawm lub lens varifocal yog tias nws tuaj yeem defocus dhau sijhawm vim muaj kev cuam tshuam los ntawm kev siv tshuab lossis thermal. Yog li ntawd, yuav tsum tau hloov kho ntxiv tom qab ob peb lub hlis.
Qhov thib plaub qhov tsis zoo yog tus nqi ntawm lub lens,nws kim tshaj qhov qub.
Summarizing, cia peb hais tias varifocal lo ntsiab muag, txawm tias lawv cov shortcomings, yog heev nrov thiab nyob rau hauv kev thov ntau dua li qhov ruaj. Txawm li cas los xij, nws tsim nyog sau cia tias qhov kev tshuaj xyuas hauv kab lus no tsuas yog rau cov koob yees duab tsim los rau kev soj ntsuam video, vim tias tsuas yog lawv muaj kev xaiv ntawm qhov ruaj los yog kho qhov muag lo ntsiab muag. Cov koob yees duab thiab cov neeg siv koob yees duab siv cov khoom siv kho qhov muag tshwj xeeb.
