Rau hnub tim ua ntej koj muas tus optics ntawm ntau xav nyob rau hauv cov nqe lus nug ntawm yuav ua li cas mus xyuas thaum yuav ib lub lens. Xwb, peb yuav tsum coj tiag nyob rau hauv tus txheej txheem no. Rau txhua system, thiab cov koob yees duab, muaj cov dozens ntawm txawv variants ntawm lo ntsiab muag ntawm lub lag luam, xws li los ntawm ib tug coj $ 50 mus rau $ 10 000 (piv txwv li: Canon telephoto). Koj khom lub tsheb koj xav tau kev pab - qhov no yog thawj kauj ruam mus rau yuav lo ntsiab muag. Peb yuav tsum tau mus kom meej meej txiav txim siab li cas koj yuav tua. Nug koj tus kheej cov lus nug zoo li nram qab ... - Kuv Yuav tua hauv tsev los yog nraum zoov? - Kuv puas yuav tau coj cov duab ntawm ceev ceev mus khoom (xws li, cov kev ua si)? - Kuv xav mus tua portraits los yog ua ib tug kab tshoob? - Kuv nyiam mus tua tsiaj qus thiab cov xwm? - Ua txhaj tshuaj ntawm ua hauj lwm, architecture los yog interiors? Cov no yog cov lus nug uas koj yuav tsum nug koj tus kheej, thiab txiav txim siab rau nws tus kheej kev siv nyiaj. Yog hais tias koj yuav npaj mus yuav ib cov SLR (DSLR), ces, raws li ib feem ntawm ib cov khoom, koj yuav twb muaj qhov yooj yim lens, uas ua rau zoo zoo nkauj cov duab. Txawm li cas los, lub ntsiab attraction ntawm no hom ntawm cov koob yees duab yog tseem mus hloov lub lens kom tau qhov zoo tshaj plaws ncej nyob rau hauv txhua txhua qhov teeb meem no. Qhov tseem ceeb cov lus nug yog: ua li cas koj nrhiav tau rau ib txoj kev rau koj xav tau kev pab?
to taub iav
Ua ntej koj yuav mus saib thaum nriav ib tug lens, nws yog tsim nyog los nkag siab txog dab tsi ua rau ib tug lens thiab yuav ua li cas nws txawv los ntawm lwm yam, nws yog thawj tsim nyog los paub ib tug ob peb tswv yim. Lub focal ntev, technically hais lus - yog lub focal ntev ntawm lub lens, sawv cev nyob rau hauv millimeters, uas yog ib tug deb ntawm lub rear hom phiaj lens mus rau lub focal dav hlau qhov chaw uas thaum uas tig mus sab ntawm lub teeb teeb meem rau lub lens sib ntawm ib tug taw tes. Nws yog ib qho tseem ceeb rau koj, vim hais tias cov focal ntev txiav txim lub kaum sab xis ntawm saib ntawm lub lens. Tus me dua cov focal ntev, lub dav lub tshav pob ntawm view. Thaum koj zoom nyob rau hauv, lub teb uas tsis pom kev narrows, ces koj yuav tau tsawg dua ntawm tus kwv, uas zoo loj nyob rau hauv kev sib raug zoo rau lub cheeb tsam. Nyob rau hauv lub ntiaj teb no ntawm tsoos 35 hli zaj duab xis, cov focal lengths ntawm 16 hli los 35 hli, yog feem ntau yog dav lub. 50-hli lens, xa mus rau raws li "ib txwm", vim hais tias cov lo ntsiab muag yog heev uas zoo sib xws rau lub xaav ntawm tus tib neeg qhov muag, thiab txhua yam uas hais saum toj no 100 hli, nws yog suav tias yog telephoto. Txawm li cas los, lub focal ntev ib tug me ntsis nyuab thaum nws los txog rau DSLRs. Qhov no yog vim hais tias cov duab sensors ntawm cov koob yees duab yog tsawg tshaj li 35 hli zaj duab xis, yog li lawv txiav ib feem ntawm cov duab thiab muab cov nyhuv ntawm ib tug ntev focal ntev. Yuav kom tau txais ib lub tswv yim ntawm yuav ua li cas no tsis sib xws yuav cuam tshuam rau lub kaum sab xis ntawm saib ntawm lub lens, nws yog tsim nyog los muab sau ntawm koj cov koob yees duab. Nikon D40, piv txwv li, ib tug qoob loo zoo tshaj ntawm 1.5 x. Raws li ib tug tshwm sim, ib tug 35 hli lens muaj ib tug teb pom ntawm 52 hli yog sib npaug thaum muab tso rau hauv D40.
diaphragm
Lwm tseem ceeb ceeb ntawm yuav ua li cas mus xyuas thaum yuav ib lub lens, ib tug diaphragm. Qhov no aperture yog ib tug mechanism uas tswj cov nyiaj ntawm lub teeb uas kis tau los ntawm cov duab khaws lens. Lub diaphragm feem ntau hu ua nyob rau hauv cov nqe lus ntawm F-nres, thiab sawv cev rau ib tug xov tooj xws li f / 2.8. Tus me tus xov tooj, tus loj dua cov qhov, thiab cov ntau lub teeb uas nkag mus rau cov koob yees duab. Lub lens ntawm lub koob yees duab, uas yuav qhib ib tug dav aperture ua rau nws ua tau rau kom muaj ib tug ntau dua shutter speeds nyob rau hauv tsawg lub teeb tej yam kev mob. Qhov no yuav ua tau qhov tseem ceeb kom tau ib tug ntse duab nrog ib tug handheld lub koob yees duab. Dav apertures kuj muab ib tug zoo tswv yim txoj kev ywj pheej, uas koj mus pov rau hauv lub keeb kwm yav dhau tawm kom pom tseeb. Ua ntej koj yuav mus saib thaum nriav ib tug lens, nrog ib tug to taub cov neeg, raws li lub khw neeg ua hauj lwm tsis yog ib txwm muaj peev xwm nyob rau hauv cov teeb meem. Yog li, koj yuav tau txuag koj lub sij hawm thiab nyiaj txiag.